[RFC] Don't block on finishing demangling msymbols

Instead, do it all on a background thread and only block when we actually need the result. Note, this is a speedup but not quite as much as I was expecting; still looking into what causes the waits. However, let me know if you have thoughts on the concept! Change-Id: I9d871917459ece0b41d31670b3c56600757aea66
Create a correctly-sized demangled names hashtable
2025-11-16 12:34:43 +00:00 · 2019-11-18 17:51:10 -06:00 · 2019-11-18 17:51:10 -06:00 · 2019-11-10 12:30:24 -06:00 · 2019-11-10 12:30:24 -06:00 · 2019-11-10 10:44:50 -07:00
38 changed files with 3080 additions and 247 deletions
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,109 @@
+2019-10-19  Tom Tromey  <tom@tromey.com>
+
+	* gdbsupport/thread-pool.c (thread_pool::set_thread_count): Set
+	name of worker thread.
+	* gdbsupport/common.m4 (GDB_AC_COMMON): Check for
+	pthread_setname_np.
+	* configure, config.in: Rebuild.
+
+2019-10-19  Tom Tromey  <tom@tromey.com>
+
+	* python/python.c (class gdbpy_gil): New.
+	(struct gdbpy_event): Add constructor, destructor, operator().
+	(gdbpy_post_event): Use run_on_main_thread.
+	(gdbpy_initialize_events): Remove.
+	(do_start_initialization): Update.
+
+2019-10-19  Tom Tromey  <tom@tromey.com>
+
+	* NEWS: Add entry.
+	* maint.c (_initialize_maint_cmds): Add "worker-threads" maint
+	commands.  Call update_thread_pool_size.
+	(update_thread_pool_size, maintenance_set_worker_threads): New
+	functions.
+	(n_worker_threads): New global.
+
+2019-10-19  Christian Biesinger  <cbiesinger@google.com>
+	    Tom Tromey  <tom@tromey.com>
+
+	* minsyms.c (minimal_symbol_reader::install): Use
+	parallel_for_each.
+	* gdbsupport/parallel-for.h: New file.
+	* Makefile.in (HFILES_NO_SRCDIR): Add gdbsupport/parallel-for.h.
+
+2019-10-19  Christian Biesinger  <cbiesinger@google.com>
+	    Tom Tromey  <tom@tromey.com>
+
+	* gdbsupport/thread-pool.h: New file.
+	* gdbsupport/thread-pool.c: New file.
+	* Makefile.in (COMMON_SFILES): Add thread-pool.c.
+	(HFILES_NO_SRCDIR): Add thread-pool.h.
+
+2019-10-19  Tom Tromey  <tom@tromey.com>
+
+	* event-top.h (thread_local_segv_handler): Declare.
+	* event-top.c (thread_local_segv_handler): New global.
+	(install_handle_sigsegv, handle_sigsegv): New functions.
+	(async_init_signals): Install SIGSEGV handler.
+	* cp-support.c (gdb_demangle_jmp_buf): Change type.  Now
+	thread-local.
+	(report_failed_demangle): New function.
+	(gdb_demangle): Make core_dump_allowed atomic.  Remove signal
+	handler-setting code, instead use segv_handler.  Run warning code
+	on main thread.
+
+2019-10-19  Tom Tromey  <tom@tromey.com>
+
+	* unittests/main-thread-selftests.c: New file.
+	* Makefile.in (SUBDIR_UNITTESTS_SRCS): Add
+	main-thread-selftests.c.
+	* ser-event.h (run_on_main_thread): Declare.
+	* ser-event.c (runnable_event, runnables, runnable_mutex): New
+	globals.
+	(run_events, run_on_main_thread, _initialize_ser_event): New
+	functions.
+
+2019-10-19  Tom Tromey  <tom@tromey.com>
+
+	* main.c (setup_alternate_signal_stack): Remove.
+	(captured_main_1): Use gdb::alternate_signal_stack.
+	* gdbsupport/alt-stack.h: New file.
+
+2019-10-19  Tom Tromey  <tom@tromey.com>
+
+	* gdbsupport/signals-state-save-restore.c (original_signal_mask):
+	Remove comment.
+	(save_original_signals_state, restore_original_signals_state): Use
+	gdb_sigmask.
+	* linux-nat.c (block_child_signals, restore_child_signals_mask)
+	(_initialize_linux_nat): Use gdb_sigmask.
+	* guile/guile.c (_initialize_guile): Use block_signals.
+	* Makefile.in (HFILES_NO_SRCDIR): Add gdb-sigmask.h.
+	* gdbsupport/gdb-sigmask.h: New file.
+	* event-top.c (async_sigtstp_handler): Use gdb_sigmask.
+	* cp-support.c (gdb_demangle): Use gdb_sigmask.
+	* gdbsupport/common.m4 (GDB_AC_COMMON): Check for
+	pthread_sigmask.
+	* configure, config.in: Rebuild.
+	* gdbsupport/block-signals.h: New file.
+
+2019-10-19  Tom Tromey  <tom@tromey.com>
+
+	* acinclude.m4: Include ax_pthread.m4.
+	* Makefile.in (PTHREAD_CFLAGS, PTHREAD_LIBS): New variables.
+	(INTERNAL_CFLAGS_BASE): Use PTHREAD_CFLAGS.
+	(CLIBS): Use PTHREAD_LIBS.
+	(aclocal_m4_deps): Add ax_pthread.m4.
+	* config.in, configure: Rebuild.
+	* gdbsupport/common.m4 (GDB_AC_COMMON): Check for std::thread.
+
+2019-10-19  Tom Tromey  <tom@tromey.com>
+
+	* symtab.h (struct minimal_symbol) <name_set>: New member.
+	* minsyms.c (minimal_symbol_reader::record_full): Copy name.
+	Don't call symbol_set_names.
+	(minimal_symbol_reader::install): Call symbol_set_names.
+
 2019-11-10  Tom Tromey  <tom@tromey.com>

 	* tui/tui-wingeneral.c (tui_unhighlight_win): Use can_box.
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -210,6 +210,9 @@ WERROR_CFLAGS = @WERROR_CFLAGS@
 GDB_WARN_CFLAGS = $(WARN_CFLAGS)
 GDB_WERROR_CFLAGS = $(WERROR_CFLAGS)

+PTHREAD_CFLAGS = @PTHREAD_CFLAGS@
+PTHREAD_LIBS = @PTHREAD_LIBS@
+
 RDYNAMIC = @RDYNAMIC@

 # Where is the INTL library?  Typically in ../intl.
@@ -430,6 +433,7 @@ SUBDIR_UNITTESTS_SRCS = \
 	unittests/optional-selftests.c \
 	unittests/parse-connection-spec-selftests.c \
 	unittests/ptid-selftests.c \
+	unittests/main-thread-selftests.c \
 	unittests/mkdir-recursive-selftests.c \
 	unittests/rsp-low-selftests.c \
 	unittests/scoped_fd-selftests.c \
@@ -580,7 +584,7 @@ INTERNAL_CFLAGS_BASE = \
 	$(GDB_CFLAGS) $(OPCODES_CFLAGS) $(READLINE_CFLAGS) $(ZLIBINC) \
 	$(BFD_CFLAGS) $(INCLUDE_CFLAGS) $(LIBDECNUMBER_CFLAGS) \
 	$(INTL_CFLAGS) $(INCGNU) $(ENABLE_CFLAGS) $(INTERNAL_CPPFLAGS) \
-	$(SRCHIGH_CFLAGS) $(TOP_CFLAGS)
+	$(SRCHIGH_CFLAGS) $(TOP_CFLAGS) $(PTHREAD_CFLAGS)
 INTERNAL_WARN_CFLAGS = $(INTERNAL_CFLAGS_BASE) $(GDB_WARN_CFLAGS)
 INTERNAL_CFLAGS = $(INTERNAL_WARN_CFLAGS) $(GDB_WERROR_CFLAGS)

@@ -594,7 +598,7 @@ LDFLAGS = @LDFLAGS@
 # PROFILE_CFLAGS is _not_ included, however, because we use monstartup.
 INTERNAL_LDFLAGS = \
 	$(CXXFLAGS) $(GLOBAL_CFLAGS) $(MH_LDFLAGS) \
-	$(LDFLAGS) $(CONFIG_LDFLAGS)
+	$(LDFLAGS) $(CONFIG_LDFLAGS) $(PTHREAD_CFLAGS)

 # Libraries and corresponding dependencies for compiling gdb.
 # XM_CLIBS, defined in *config files, have host-dependent libs.
@@ -605,7 +609,7 @@ CLIBS = $(SIM) $(READLINE) $(OPCODES) $(BFD) $(LIBCTF) $(ZLIB) \
 	@LIBS@ @GUILE_LIBS@ @PYTHON_LIBS@ \
 	$(LIBEXPAT) $(LIBLZMA) $(LIBBABELTRACE) $(LIBIPT) \
 	$(LIBIBERTY) $(WIN32LIBS) $(LIBGNU) $(LIBICONV) $(LIBMPFR) \
-	$(SRCHIGH_LIBS) $(LIBXXHASH)
+	$(SRCHIGH_LIBS) $(LIBXXHASH) $(PTHREAD_LIBS)
 CDEPS = $(NAT_CDEPS) $(SIM) $(BFD) $(READLINE_DEPS) $(LIBCTF) \
 	$(OPCODES) $(INTL_DEPS) $(LIBIBERTY) $(CONFIG_DEPS) $(LIBGNU)

@@ -989,6 +993,7 @@ COMMON_SFILES = \
 	gdbsupport/signals.c \
 	gdbsupport/signals-state-save-restore.c \
 	gdbsupport/tdesc.c \
+	gdbsupport/thread-pool.c \
 	gdbsupport/xml-utils.c \
 	complaints.c \
 	completer.c \
@@ -1468,6 +1473,7 @@ HFILES_NO_SRCDIR = \
 	gdbsupport/fileio.h \
 	gdbsupport/format.h \
 	gdbsupport/gdb-dlfcn.h \
+	gdbsupport/gdb-sigmask.h \
 	gdbsupport/gdb_assert.h \
 	gdbsupport/gdb_binary_search.h \
 	gdbsupport/gdb_tilde_expand.h \
@@ -1481,6 +1487,7 @@ HFILES_NO_SRCDIR = \
 	gdbsupport/common-inferior.h \
 	gdbsupport/netstuff.h \
 	gdbsupport/host-defs.h \
+	gdbsupport/parallel-for.h \
 	gdbsupport/pathstuff.h \
 	gdbsupport/print-utils.h \
 	gdbsupport/ptid.h \
@@ -1490,6 +1497,7 @@ HFILES_NO_SRCDIR = \
 	gdbsupport/signals-state-save-restore.h \
 	gdbsupport/symbol.h \
 	gdbsupport/tdesc.h \
+	gdbsupport/thread-pool.h \
 	gdbsupport/version.h \
 	gdbsupport/x86-xstate.h \
 	gdbsupport/xml-utils.h \
@@ -2061,7 +2069,8 @@ aclocal_m4_deps = \
 	../config/depstand.m4 \
 	../config/lcmessage.m4 \
 	../config/codeset.m4 \
-	../config/zlib.m4
+	../config/zlib.m4 \
+	../config/ax_pthread.m4

 $(srcdir)/aclocal.m4: @MAINTAINER_MODE_TRUE@ $(aclocal_m4_deps)
 	cd $(srcdir) && $(ACLOCAL) $(ACLOCAL_AMFLAGS)
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -146,6 +146,13 @@ set style highlight background COLOR
 set style highlight intensity VALUE
  Control the styling of highlightings.

+maint set worker-threads
+maint show worker-threads
+  Control the number of worker threads that can be used by GDB.  The
+  default is "unlimited", which lets GDB choose a number that is
+  reasonable.  Currently worker threads are only used when demangling
+  the names of linker symbols.
+
 maint set test-settings KIND
 maint show test-settings KIND
  A set of commands used by the testsuite for exercising the settings
--- a/gdb/acinclude.m4
+++ b/gdb/acinclude.m4
@@ -73,6 +73,8 @@ m4_include(ptrace.m4)

 m4_include(ax_cxx_compile_stdcxx.m4)

+m4_include([../config/ax_pthread.m4])
+
 ## ----------------------------------------- ##
 ## ANSIfy the C compiler whenever possible.  ##
 ## From Franc,ois Pinard                     ##
--- a/gdb/config.in
+++ b/gdb/config.in
@@ -17,6 +17,9 @@
   */
 #undef CRAY_STACKSEG_END

+/* Define to 1 if std::thread works. */
+#undef CXX_STD_THREAD
+
 /* Define to 1 if using `alloca.c'. */
 #undef C_ALLOCA

@@ -336,6 +339,15 @@
 /* Define if <sys/procfs.h> has psaddr_t. */
 #undef HAVE_PSADDR_T

+/* Have PTHREAD_PRIO_INHERIT. */
+#undef HAVE_PTHREAD_PRIO_INHERIT
+
+/* Define to 1 if you have the `pthread_setname_np' function. */
+#undef HAVE_PTHREAD_SETNAME_NP
+
+/* Define to 1 if you have the `pthread_sigmask' function. */
+#undef HAVE_PTHREAD_SIGMASK
+
 /* Define to 1 if you have the `ptrace64' function. */
 #undef HAVE_PTRACE64

@@ -625,6 +637,10 @@
 /* Define to 1 if the "%ll" format works to print long longs. */
 #undef PRINTF_HAS_LONG_LONG

+/* Define to necessary symbol if this constant uses a non-standard name on
+   your system. */
+#undef PTHREAD_CREATE_JOINABLE
+
 /* Define to the type of arg 1 for ptrace. */
 #undef PTRACE_TYPE_ARG1

--- a/gdb/configure
+++ b/gdb/configure
@@ -702,6 +702,11 @@ SYSTEM_GDBINIT
 TARGET_SYSTEM_ROOT
 CONFIG_LDFLAGS
 RDYNAMIC
+PTHREAD_CFLAGS
+PTHREAD_LIBS
+PTHREAD_CC
+ax_pthread_config
+SED
 ALLOCA
 LTLIBIPT
 LIBIPT
@@ -2515,6 +2520,73 @@ fi
  as_fn_set_status $ac_retval

 } # ac_fn_cxx_try_link
+
+# ac_fn_cxx_check_func LINENO FUNC VAR
+# ------------------------------------
+# Tests whether FUNC exists, setting the cache variable VAR accordingly
+ac_fn_cxx_check_func ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for $2" >&5
+$as_echo_n "checking for $2... " >&6; }
+if eval \${$3+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+/* Define $2 to an innocuous variant, in case <limits.h> declares $2.
+   For example, HP-UX 11i <limits.h> declares gettimeofday.  */
+#define $2 innocuous_$2
+
+/* System header to define __stub macros and hopefully few prototypes,
+    which can conflict with char $2 (); below.
+    Prefer <limits.h> to <assert.h> if __STDC__ is defined, since
+    <limits.h> exists even on freestanding compilers.  */
+
+#ifdef __STDC__
+# include <limits.h>
+#else
+# include <assert.h>
+#endif
+
+#undef $2
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char $2 ();
+/* The GNU C library defines this for functions which it implements
+    to always fail with ENOSYS.  Some functions are actually named
+    something starting with __ and the normal name is an alias.  */
+#if defined __stub_$2 || defined __stub___$2
+choke me
+#endif
+
+int
+main ()
+{
+return $2 ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+  eval "$3=yes"
+else
+  eval "$3=no"
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+fi
+eval ac_res=\$$3
+	       { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
+$as_echo "$ac_res" >&6; }
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+
+} # ac_fn_cxx_check_func
 cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
@@ -13130,6 +13202,75 @@ _ACEOF

 fi

+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for a sed that does not truncate output" >&5
+$as_echo_n "checking for a sed that does not truncate output... " >&6; }
+if ${ac_cv_path_SED+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+            ac_script=s/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb/
+     for ac_i in 1 2 3 4 5 6 7; do
+       ac_script="$ac_script$as_nl$ac_script"
+     done
+     echo "$ac_script" 2>/dev/null | sed 99q >conftest.sed
+     { ac_script=; unset ac_script;}
+     if test -z "$SED"; then
+  ac_path_SED_found=false
+  # Loop through the user's path and test for each of PROGNAME-LIST
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_prog in sed gsed; do
+    for ac_exec_ext in '' $ac_executable_extensions; do
+      ac_path_SED="$as_dir/$ac_prog$ac_exec_ext"
+      as_fn_executable_p "$ac_path_SED" || continue
+# Check for GNU ac_path_SED and select it if it is found.
+  # Check for GNU $ac_path_SED
+case `"$ac_path_SED" --version 2>&1` in
+*GNU*)
+  ac_cv_path_SED="$ac_path_SED" ac_path_SED_found=:;;
+*)
+  ac_count=0
+  $as_echo_n 0123456789 >"conftest.in"
+  while :
+  do
+    cat "conftest.in" "conftest.in" >"conftest.tmp"
+    mv "conftest.tmp" "conftest.in"
+    cp "conftest.in" "conftest.nl"
+    $as_echo '' >> "conftest.nl"
+    "$ac_path_SED" -f conftest.sed < "conftest.nl" >"conftest.out" 2>/dev/null || break
+    diff "conftest.out" "conftest.nl" >/dev/null 2>&1 || break
+    as_fn_arith $ac_count + 1 && ac_count=$as_val
+    if test $ac_count -gt ${ac_path_SED_max-0}; then
+      # Best one so far, save it but keep looking for a better one
+      ac_cv_path_SED="$ac_path_SED"
+      ac_path_SED_max=$ac_count
+    fi
+    # 10*(2^10) chars as input seems more than enough
+    test $ac_count -gt 10 && break
+  done
+  rm -f conftest.in conftest.tmp conftest.nl conftest.out;;
+esac
+
+      $ac_path_SED_found && break 3
+    done
+  done
+  done
+IFS=$as_save_IFS
+  if test -z "$ac_cv_path_SED"; then
+    as_fn_error $? "no acceptable sed could be found in \$PATH" "$LINENO" 5
+  fi
+else
+  ac_cv_path_SED=$SED
+fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_path_SED" >&5
+$as_echo "$ac_cv_path_SED" >&6; }
+ SED="$ac_cv_path_SED"
+  rm -f conftest.sed
+

  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ANSI C header files" >&5
 $as_echo_n "checking for ANSI C header files... " >&6; }
@@ -13515,6 +13656,715 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF


+  # Check for std::thread.  This does not work on some platforms, like
+  # mingw and DJGPP.
+  ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+
+
+
+
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+ax_pthread_ok=no
+
+# We used to check for pthread.h first, but this fails if pthread.h
+# requires special compiler flags (e.g. on Tru64 or Sequent).
+# It gets checked for in the link test anyway.
+
+# First of all, check if the user has set any of the PTHREAD_LIBS,
+# etcetera environment variables, and if threads linking works using
+# them:
+if test "x$PTHREAD_CFLAGS$PTHREAD_LIBS" != "x"; then
+        ax_pthread_save_CC="$CC"
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        if test "x$PTHREAD_CC" != "x"; then :
+  CC="$PTHREAD_CC"
+fi
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS" >&5
+$as_echo_n "checking for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS... " >&6; }
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char pthread_join ();
+int
+main ()
+{
+return pthread_join ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_pthread_ok=yes
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_ok" >&5
+$as_echo "$ax_pthread_ok" >&6; }
+        if test "x$ax_pthread_ok" = "xno"; then
+                PTHREAD_LIBS=""
+                PTHREAD_CFLAGS=""
+        fi
+        CC="$ax_pthread_save_CC"
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+fi
+
+# We must check for the threads library under a number of different
+# names; the ordering is very important because some systems
+# (e.g. DEC) have both -lpthread and -lpthreads, where one of the
+# libraries is broken (non-POSIX).
+
+# Create a list of thread flags to try.  Items starting with a "-" are
+# C compiler flags, and other items are library names, except for "none"
+# which indicates that we try without any flags at all, and "pthread-config"
+# which is a program returning the flags for the Pth emulation library.
+
+ax_pthread_flags="pthreads none -Kthread -pthread -pthreads -mthreads pthread --thread-safe -mt pthread-config"
+
+# The ordering *is* (sometimes) important.  Some notes on the
+# individual items follow:
+
+# pthreads: AIX (must check this before -lpthread)
+# none: in case threads are in libc; should be tried before -Kthread and
+#       other compiler flags to prevent continual compiler warnings
+# -Kthread: Sequent (threads in libc, but -Kthread needed for pthread.h)
+# -pthread: Linux/gcc (kernel threads), BSD/gcc (userland threads), Tru64
+#           (Note: HP C rejects this with "bad form for `-t' option")
+# -pthreads: Solaris/gcc (Note: HP C also rejects)
+# -mt: Sun Workshop C (may only link SunOS threads [-lthread], but it
+#      doesn't hurt to check since this sometimes defines pthreads and
+#      -D_REENTRANT too), HP C (must be checked before -lpthread, which
+#      is present but should not be used directly; and before -mthreads,
+#      because the compiler interprets this as "-mt" + "-hreads")
+# -mthreads: Mingw32/gcc, Lynx/gcc
+# pthread: Linux, etcetera
+# --thread-safe: KAI C++
+# pthread-config: use pthread-config program (for GNU Pth library)
+
+case $host_os in
+
+        freebsd*)
+
+        # -kthread: FreeBSD kernel threads (preferred to -pthread since SMP-able)
+        # lthread: LinuxThreads port on FreeBSD (also preferred to -pthread)
+
+        ax_pthread_flags="-kthread lthread $ax_pthread_flags"
+        ;;
+
+        hpux*)
+
+        # From the cc(1) man page: "[-mt] Sets various -D flags to enable
+        # multi-threading and also sets -lpthread."
+
+        ax_pthread_flags="-mt -pthread pthread $ax_pthread_flags"
+        ;;
+
+        openedition*)
+
+        # IBM z/OS requires a feature-test macro to be defined in order to
+        # enable POSIX threads at all, so give the user a hint if this is
+        # not set. (We don't define these ourselves, as they can affect
+        # other portions of the system API in unpredictable ways.)
+
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#            if !defined(_OPEN_THREADS) && !defined(_UNIX03_THREADS)
+             AX_PTHREAD_ZOS_MISSING
+#            endif
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "AX_PTHREAD_ZOS_MISSING" >/dev/null 2>&1; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support." >&5
+$as_echo "$as_me: WARNING: IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support." >&2;}
+fi
+rm -f conftest*
+
+        ;;
+
+        solaris*)
+
+        # On Solaris (at least, for some versions), libc contains stubbed
+        # (non-functional) versions of the pthreads routines, so link-based
+        # tests will erroneously succeed. (N.B.: The stubs are missing
+        # pthread_cleanup_push, or rather a function called by this macro,
+        # so we could check for that, but who knows whether they'll stub
+        # that too in a future libc.)  So we'll check first for the
+        # standard Solaris way of linking pthreads (-mt -lpthread).
+
+        ax_pthread_flags="-mt,pthread pthread $ax_pthread_flags"
+        ;;
+esac
+
+# GCC generally uses -pthread, or -pthreads on some platforms (e.g. SPARC)
+
+if test "x$GCC" = "xyes"; then :
+  ax_pthread_flags="-pthread -pthreads $ax_pthread_flags"
+fi
+
+# The presence of a feature test macro requesting re-entrant function
+# definitions is, on some systems, a strong hint that pthreads support is
+# correctly enabled
+
+case $host_os in
+        darwin* | hpux* | linux* | osf* | solaris*)
+        ax_pthread_check_macro="_REENTRANT"
+        ;;
+
+        aix*)
+        ax_pthread_check_macro="_THREAD_SAFE"
+        ;;
+
+        *)
+        ax_pthread_check_macro="--"
+        ;;
+esac
+if test "x$ax_pthread_check_macro" = "x--"; then :
+  ax_pthread_check_cond=0
+else
+  ax_pthread_check_cond="!defined($ax_pthread_check_macro)"
+fi
+
+# Are we compiling with Clang?
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC is Clang" >&5
+$as_echo_n "checking whether $CC is Clang... " >&6; }
+if ${ax_cv_PTHREAD_CLANG+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_CLANG=no
+     # Note that Autoconf sets GCC=yes for Clang as well as GCC
+     if test "x$GCC" = "xyes"; then
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+/* Note: Clang 2.7 lacks __clang_[a-z]+__ */
+#            if defined(__clang__) && defined(__llvm__)
+             AX_PTHREAD_CC_IS_CLANG
+#            endif
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "AX_PTHREAD_CC_IS_CLANG" >/dev/null 2>&1; then :
+  ax_cv_PTHREAD_CLANG=yes
+fi
+rm -f conftest*
+
+     fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_CLANG" >&5
+$as_echo "$ax_cv_PTHREAD_CLANG" >&6; }
+ax_pthread_clang="$ax_cv_PTHREAD_CLANG"
+
+ax_pthread_clang_warning=no
+
+# Clang needs special handling, because older versions handle the -pthread
+# option in a rather... idiosyncratic way
+
+if test "x$ax_pthread_clang" = "xyes"; then
+
+        # Clang takes -pthread; it has never supported any other flag
+
+        # (Note 1: This will need to be revisited if a system that Clang
+        # supports has POSIX threads in a separate library.  This tends not
+        # to be the way of modern systems, but it's conceivable.)
+
+        # (Note 2: On some systems, notably Darwin, -pthread is not needed
+        # to get POSIX threads support; the API is always present and
+        # active.  We could reasonably leave PTHREAD_CFLAGS empty.  But
+        # -pthread does define _REENTRANT, and while the Darwin headers
+        # ignore this macro, third-party headers might not.)
+
+        PTHREAD_CFLAGS="-pthread"
+        PTHREAD_LIBS=
+
+        ax_pthread_ok=yes
+
+        # However, older versions of Clang make a point of warning the user
+        # that, in an invocation where only linking and no compilation is
+        # taking place, the -pthread option has no effect ("argument unused
+        # during compilation").  They expect -pthread to be passed in only
+        # when source code is being compiled.
+        #
+        # Problem is, this is at odds with the way Automake and most other
+        # C build frameworks function, which is that the same flags used in
+        # compilation (CFLAGS) are also used in linking.  Many systems
+        # supported by AX_PTHREAD require exactly this for POSIX threads
+        # support, and in fact it is often not straightforward to specify a
+        # flag that is used only in the compilation phase and not in
+        # linking.  Such a scenario is extremely rare in practice.
+        #
+        # Even though use of the -pthread flag in linking would only print
+        # a warning, this can be a nuisance for well-run software projects
+        # that build with -Werror.  So if the active version of Clang has
+        # this misfeature, we search for an option to squash it.
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether Clang needs flag to prevent \"argument unused\" warning when linking with -pthread" >&5
+$as_echo_n "checking whether Clang needs flag to prevent \"argument unused\" warning when linking with -pthread... " >&6; }
+if ${ax_cv_PTHREAD_CLANG_NO_WARN_FLAG+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_CLANG_NO_WARN_FLAG=unknown
+             # Create an alternate version of $ac_link that compiles and
+             # links in two steps (.c -> .o, .o -> exe) instead of one
+             # (.c -> exe), because the warning occurs only in the second
+             # step
+             ax_pthread_save_ac_link="$ac_link"
+             ax_pthread_sed='s/conftest\.\$ac_ext/conftest.$ac_objext/g'
+             ax_pthread_link_step=`$as_echo "$ac_link" | sed "$ax_pthread_sed"`
+             ax_pthread_2step_ac_link="($ac_compile) && (echo ==== >&5) && ($ax_pthread_link_step)"
+             ax_pthread_save_CFLAGS="$CFLAGS"
+             for ax_pthread_try in '' -Qunused-arguments -Wno-unused-command-line-argument unknown; do
+                if test "x$ax_pthread_try" = "xunknown"; then :
+  break
+fi
+                CFLAGS="-Werror -Wunknown-warning-option $ax_pthread_try -pthread $ax_pthread_save_CFLAGS"
+                ac_link="$ax_pthread_save_ac_link"
+                cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+int main(void){return 0;}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_link="$ax_pthread_2step_ac_link"
+                     cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+int main(void){return 0;}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  break
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+             done
+             ac_link="$ax_pthread_save_ac_link"
+             CFLAGS="$ax_pthread_save_CFLAGS"
+             if test "x$ax_pthread_try" = "x"; then :
+  ax_pthread_try=no
+fi
+             ax_cv_PTHREAD_CLANG_NO_WARN_FLAG="$ax_pthread_try"
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" >&5
+$as_echo "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" >&6; }
+
+        case "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" in
+                no | unknown) ;;
+                *) PTHREAD_CFLAGS="$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG $PTHREAD_CFLAGS" ;;
+        esac
+
+fi # $ax_pthread_clang = yes
+
+if test "x$ax_pthread_ok" = "xno"; then
+for ax_pthread_try_flag in $ax_pthread_flags; do
+
+        case $ax_pthread_try_flag in
+                none)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work without any flags" >&5
+$as_echo_n "checking whether pthreads work without any flags... " >&6; }
+                ;;
+
+                -mt,pthread)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work with -mt -lpthread" >&5
+$as_echo_n "checking whether pthreads work with -mt -lpthread... " >&6; }
+                PTHREAD_CFLAGS="-mt"
+                PTHREAD_LIBS="-lpthread"
+                ;;
+
+                -*)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work with $ax_pthread_try_flag" >&5
+$as_echo_n "checking whether pthreads work with $ax_pthread_try_flag... " >&6; }
+                PTHREAD_CFLAGS="$ax_pthread_try_flag"
+                ;;
+
+                pthread-config)
+                # Extract the first word of "pthread-config", so it can be a program name with args.
+set dummy pthread-config; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_prog_ax_pthread_config+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$ax_pthread_config"; then
+  ac_cv_prog_ax_pthread_config="$ax_pthread_config" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_ax_pthread_config="yes"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  test -z "$ac_cv_prog_ax_pthread_config" && ac_cv_prog_ax_pthread_config="no"
+fi
+fi
+ax_pthread_config=$ac_cv_prog_ax_pthread_config
+if test -n "$ax_pthread_config"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_config" >&5
+$as_echo "$ax_pthread_config" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+                if test "x$ax_pthread_config" = "xno"; then :
+  continue
+fi
+                PTHREAD_CFLAGS="`pthread-config --cflags`"
+                PTHREAD_LIBS="`pthread-config --ldflags` `pthread-config --libs`"
+                ;;
+
+                *)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking for the pthreads library -l$ax_pthread_try_flag" >&5
+$as_echo_n "checking for the pthreads library -l$ax_pthread_try_flag... " >&6; }
+                PTHREAD_LIBS="-l$ax_pthread_try_flag"
+                ;;
+        esac
+
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Check for various functions.  We must include pthread.h,
+        # since some functions may be macros.  (On the Sequent, we
+        # need a special flag -Kthread to make this header compile.)
+        # We check for pthread_join because it is in -lpthread on IRIX
+        # while pthread_create is in libc.  We check for pthread_attr_init
+        # due to DEC craziness with -lpthreads.  We check for
+        # pthread_cleanup_push because it is one of the few pthread
+        # functions on Solaris that doesn't have a non-functional libc stub.
+        # We try pthread_create on general principles.
+
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+#                       if $ax_pthread_check_cond
+#                        error "$ax_pthread_check_macro must be defined"
+#                       endif
+                        static void routine(void *a) { a = 0; }
+                        static void *start_routine(void *a) { return a; }
+int
+main ()
+{
+pthread_t th; pthread_attr_t attr;
+                        pthread_create(&th, 0, start_routine, 0);
+                        pthread_join(th, 0);
+                        pthread_attr_init(&attr);
+                        pthread_cleanup_push(routine, 0);
+                        pthread_cleanup_pop(0) /* ; */
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_pthread_ok=yes
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_ok" >&5
+$as_echo "$ax_pthread_ok" >&6; }
+        if test "x$ax_pthread_ok" = "xyes"; then :
+  break
+fi
+
+        PTHREAD_LIBS=""
+        PTHREAD_CFLAGS=""
+done
+fi
+
+# Various other checks:
+if test "x$ax_pthread_ok" = "xyes"; then
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Detect AIX lossage: JOINABLE attribute is called UNDETACHED.
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for joinable pthread attribute" >&5
+$as_echo_n "checking for joinable pthread attribute... " >&6; }
+if ${ax_cv_PTHREAD_JOINABLE_ATTR+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_JOINABLE_ATTR=unknown
+             for ax_pthread_attr in PTHREAD_CREATE_JOINABLE PTHREAD_CREATE_UNDETACHED; do
+                 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main ()
+{
+int attr = $ax_pthread_attr; return attr /* ; */
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_cv_PTHREAD_JOINABLE_ATTR=$ax_pthread_attr; break
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+             done
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_JOINABLE_ATTR" >&5
+$as_echo "$ax_cv_PTHREAD_JOINABLE_ATTR" >&6; }
+        if test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xunknown" && \
+               test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xPTHREAD_CREATE_JOINABLE" && \
+               test "x$ax_pthread_joinable_attr_defined" != "xyes"; then :
+
+cat >>confdefs.h <<_ACEOF
+#define PTHREAD_CREATE_JOINABLE $ax_cv_PTHREAD_JOINABLE_ATTR
+_ACEOF
+
+               ax_pthread_joinable_attr_defined=yes
+
+fi
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether more special flags are required for pthreads" >&5
+$as_echo_n "checking whether more special flags are required for pthreads... " >&6; }
+if ${ax_cv_PTHREAD_SPECIAL_FLAGS+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_SPECIAL_FLAGS=no
+             case $host_os in
+             solaris*)
+             ax_cv_PTHREAD_SPECIAL_FLAGS="-D_POSIX_PTHREAD_SEMANTICS"
+             ;;
+             esac
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_SPECIAL_FLAGS" >&5
+$as_echo "$ax_cv_PTHREAD_SPECIAL_FLAGS" >&6; }
+        if test "x$ax_cv_PTHREAD_SPECIAL_FLAGS" != "xno" && \
+               test "x$ax_pthread_special_flags_added" != "xyes"; then :
+  PTHREAD_CFLAGS="$ax_cv_PTHREAD_SPECIAL_FLAGS $PTHREAD_CFLAGS"
+               ax_pthread_special_flags_added=yes
+fi
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for PTHREAD_PRIO_INHERIT" >&5
+$as_echo_n "checking for PTHREAD_PRIO_INHERIT... " >&6; }
+if ${ax_cv_PTHREAD_PRIO_INHERIT+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main ()
+{
+int i = PTHREAD_PRIO_INHERIT;
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_cv_PTHREAD_PRIO_INHERIT=yes
+else
+  ax_cv_PTHREAD_PRIO_INHERIT=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_PRIO_INHERIT" >&5
+$as_echo "$ax_cv_PTHREAD_PRIO_INHERIT" >&6; }
+        if test "x$ax_cv_PTHREAD_PRIO_INHERIT" = "xyes" && \
+               test "x$ax_pthread_prio_inherit_defined" != "xyes"; then :
+
+$as_echo "#define HAVE_PTHREAD_PRIO_INHERIT 1" >>confdefs.h
+
+               ax_pthread_prio_inherit_defined=yes
+
+fi
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        # More AIX lossage: compile with *_r variant
+        if test "x$GCC" != "xyes"; then
+            case $host_os in
+                aix*)
+                case "x/$CC" in #(
+  x*/c89|x*/c89_128|x*/c99|x*/c99_128|x*/cc|x*/cc128|x*/xlc|x*/xlc_v6|x*/xlc128|x*/xlc128_v6) :
+    #handle absolute path differently from PATH based program lookup
+                     case "x$CC" in #(
+  x/*) :
+    if as_fn_executable_p ${CC}_r; then :
+  PTHREAD_CC="${CC}_r"
+fi ;; #(
+  *) :
+    for ac_prog in ${CC}_r
+do
+  # Extract the first word of "$ac_prog", so it can be a program name with args.
+set dummy $ac_prog; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_prog_PTHREAD_CC+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$PTHREAD_CC"; then
+  ac_cv_prog_PTHREAD_CC="$PTHREAD_CC" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_PTHREAD_CC="$ac_prog"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+fi
+fi
+PTHREAD_CC=$ac_cv_prog_PTHREAD_CC
+if test -n "$PTHREAD_CC"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $PTHREAD_CC" >&5
+$as_echo "$PTHREAD_CC" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+  test -n "$PTHREAD_CC" && break
+done
+test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+ ;;
+esac ;; #(
+  *) :
+     ;;
+esac
+                ;;
+            esac
+        fi
+fi
+
+test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+
+
+
+
+
+# Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND:
+if test "x$ax_pthread_ok" = "xyes"; then
+        threads=yes
+        :
+else
+        ax_pthread_ok=no
+        threads=no
+fi
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+
+  if test "$threads" = "yes"; then
+    save_LIBS="$LIBS"
+    LIBS="$PTHREAD_LIBS $LIBS"
+    save_CXXFLAGS="$CXXFLAGS"
+    CXXFLAGS="$PTHREAD_CFLAGS $save_CFLAGS"
+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for std::thread" >&5
+$as_echo_n "checking for std::thread... " >&6; }
+if ${gdb_cv_cxx_std_thread+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <thread>
+      void callback() { }
+int
+main ()
+{
+std::thread t(callback);
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  gdb_cv_cxx_std_thread=yes
+else
+  gdb_cv_cxx_std_thread=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gdb_cv_cxx_std_thread" >&5
+$as_echo "$gdb_cv_cxx_std_thread" >&6; }
+
+    # This check must be here, while LIBS includes any necessary
+    # threading library.
+    for ac_func in pthread_sigmask pthread_setname_np
+do :
+  as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
+ac_fn_cxx_check_func "$LINENO" "$ac_func" "$as_ac_var"
+if eval test \"x\$"$as_ac_var"\" = x"yes"; then :
+  cat >>confdefs.h <<_ACEOF
+#define `$as_echo "HAVE_$ac_func" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+done
+
+
+    LIBS="$save_LIBS"
+    CXXFLAGS="$save_CXXFLAGS"
+  fi
+  if test $gdb_cv_cxx_std_thread = yes; then
+
+$as_echo "#define CXX_STD_THREAD 1" >>confdefs.h
+
+  fi
+  ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sigsetjmp" >&5
 $as_echo_n "checking for sigsetjmp... " >&6; }
 if ${gdb_cv_func_sigsetjmp+:} false; then :
--- a/gdb/cp-support.c
+++ b/gdb/cp-support.c
@@ -37,6 +37,10 @@
 #include "gdbsupport/gdb_setjmp.h"
 #include "safe-ctype.h"
 #include "gdbsupport/selftest.h"
+#include "gdbsupport/gdb-sigmask.h"
+#include <atomic>
+#include "event-top.h"
+#include "ser-event.h"

 #define d_left(dc) (dc)->u.s_binary.left
 #define d_right(dc) (dc)->u.s_binary.right
@@ -1476,11 +1480,11 @@ static bool catch_demangler_crashes = true;

 /* Stack context and environment for demangler crash recovery.  */

-static SIGJMP_BUF gdb_demangle_jmp_buf;
+static thread_local SIGJMP_BUF *gdb_demangle_jmp_buf;

 /* If nonzero, attempt to dump core from the signal handler.  */

-static int gdb_demangle_attempt_core_dump = 1;
+static std::atomic<bool> gdb_demangle_attempt_core_dump;

 /* Signal handler for gdb_demangle.  */

@@ -1492,10 +1496,46 @@ gdb_demangle_signal_handler (int signo)
      if (fork () == 0)
 	dump_core ();

-      gdb_demangle_attempt_core_dump = 0;
+      gdb_demangle_attempt_core_dump = false;
    }

-  SIGLONGJMP (gdb_demangle_jmp_buf, signo);
+  SIGLONGJMP (*gdb_demangle_jmp_buf, signo);
+}
+
+/* A helper for gdb_demangle that reports a demangling failure.  */
+
+static void
+report_failed_demangle (const char *name, bool core_dump_allowed,
+			int crash_signal)
+{
+  static bool error_reported = false;
+
+  if (!error_reported)
+    {
+      std::string short_msg
+	= string_printf (_("unable to demangle '%s' "
+			   "(demangler failed with signal %d)"),
+			 name, crash_signal);
+
+      std::string long_msg
+	= string_printf ("%s:%d: %s: %s", __FILE__, __LINE__,
+			 "demangler-warning", short_msg.c_str ());
+
+      target_terminal::scoped_restore_terminal_state term_state;
+      target_terminal::ours_for_output ();
+
+      begin_line ();
+      if (core_dump_allowed)
+	fprintf_unfiltered (gdb_stderr,
+			    _("%s\nAttempting to dump core.\n"),
+			    long_msg.c_str ());
+      else
+	warn_cant_dump_core (long_msg.c_str ());
+
+      demangler_warning (__FILE__, __LINE__, "%s", short_msg.c_str ());
+
+      error_reported = true;
+    }
 }

 #endif
@@ -1509,45 +1549,27 @@ gdb_demangle (const char *name, int options)
  int crash_signal = 0;

 #ifdef HAVE_WORKING_FORK
-#if defined (HAVE_SIGACTION) && defined (SA_RESTART)
-  struct sigaction sa, old_sa;
-#else
-  sighandler_t ofunc;
-#endif
-  static int core_dump_allowed = -1;
-
-  if (core_dump_allowed == -1)
-    {
-      core_dump_allowed = can_dump_core (LIMIT_CUR);
-
-      if (!core_dump_allowed)
-	gdb_demangle_attempt_core_dump = 0;
-    }
+  scoped_restore restore_segv
+    = make_scoped_restore (&thread_local_segv_handler,
+			   catch_demangler_crashes
+			   ? gdb_demangle_signal_handler
+			   : nullptr);

+  bool core_dump_allowed = gdb_demangle_attempt_core_dump;
+  SIGJMP_BUF jmp_buf;
+  scoped_restore restore_jmp_buf
+    = make_scoped_restore (&gdb_demangle_jmp_buf, &jmp_buf);
  if (catch_demangler_crashes)
    {
-#if defined (HAVE_SIGACTION) && defined (SA_RESTART)
-      sa.sa_handler = gdb_demangle_signal_handler;
-      sigemptyset (&sa.sa_mask);
-#ifdef HAVE_SIGALTSTACK
-      sa.sa_flags = SA_ONSTACK;
-#else
-      sa.sa_flags = 0;
-#endif
-      sigaction (SIGSEGV, &sa, &old_sa);
-#else
-      ofunc = signal (SIGSEGV, gdb_demangle_signal_handler);
-#endif
-
      /* The signal handler may keep the signal blocked when we longjmp out
         of it.  If we have sigprocmask, we can use it to unblock the signal
 	 afterwards and we can avoid the performance overhead of saving the
 	 signal mask just in case the signal gets triggered.  Otherwise, just
 	 tell sigsetjmp to save the mask.  */
 #ifdef HAVE_SIGPROCMASK
-      crash_signal = SIGSETJMP (gdb_demangle_jmp_buf, 0);
+      crash_signal = SIGSETJMP (*gdb_demangle_jmp_buf, 0);
 #else
-      crash_signal = SIGSETJMP (gdb_demangle_jmp_buf, 1);
+      crash_signal = SIGSETJMP (*gdb_demangle_jmp_buf, 1);
 #endif
    }
 #endif
@@ -1558,53 +1580,28 @@ gdb_demangle (const char *name, int options)
 #ifdef HAVE_WORKING_FORK
  if (catch_demangler_crashes)
    {
-#if defined (HAVE_SIGACTION) && defined (SA_RESTART)
-      sigaction (SIGSEGV, &old_sa, NULL);
-#else
-      signal (SIGSEGV, ofunc);
-#endif
-
      if (crash_signal != 0)
-	{
-	  static int error_reported = 0;
-
+        {
 #ifdef HAVE_SIGPROCMASK
 	  /* If we got the signal, SIGSEGV may still be blocked; restore it.  */
 	  sigset_t segv_sig_set;
 	  sigemptyset (&segv_sig_set);
 	  sigaddset (&segv_sig_set, SIGSEGV);
-	  sigprocmask (SIG_UNBLOCK, &segv_sig_set, NULL);
+	  gdb_sigmask (SIG_UNBLOCK, &segv_sig_set, NULL);
 #endif

-	  if (!error_reported)
-	    {
-	      std::string short_msg
-		= string_printf (_("unable to demangle '%s' "
-				   "(demangler failed with signal %d)"),
-				 name, crash_signal);
+	  /* If there was a failure, we can't report it here, because
+	     we might be in a background thread.  Instead, arrange for
+	     the reporting to happen on the main thread.  */
+          std::string copy = name;
+          run_on_main_thread ([=] ()
+            {
+              report_failed_demangle (copy.c_str (), core_dump_allowed,
+                                      crash_signal);
+            });

-	      std::string long_msg
-		= string_printf ("%s:%d: %s: %s", __FILE__, __LINE__,
-				 "demangler-warning", short_msg.c_str ());
-
-	      target_terminal::scoped_restore_terminal_state term_state;
-	      target_terminal::ours_for_output ();
-
-	      begin_line ();
-	      if (core_dump_allowed)
-		fprintf_unfiltered (gdb_stderr,
-				    _("%s\nAttempting to dump core.\n"),
-				    long_msg.c_str ());
-	      else
-		warn_cant_dump_core (long_msg.c_str ());
-
-	      demangler_warning (__FILE__, __LINE__, "%s", short_msg.c_str ());
-
-	      error_reported = 1;
-	    }
-
-	  result = NULL;
-	}
+          result = NULL;
+        }
    }
 #endif

@@ -2211,4 +2208,7 @@ display the offending symbol."),
  selftests::register_test ("cp_remove_params",
 			    selftests::test_cp_remove_params);
 #endif
+
+  if (!can_dump_core (LIMIT_CUR))
+    gdb_demangle_attempt_core_dump = false;
 }
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,8 @@
+2019-10-19  Tom Tromey  <tom@tromey.com>
+
+	* gdb.texinfo (Maintenance Commands): Document new maint
+	commands.
+
 2019-10-31  Andrew Burgess  <andrew.burgess@embecosm.com>

 	* gdb.texinfo (Symbols): Document new 'info module variables' and
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -37841,6 +37841,21 @@ with the DWARF frame unwinders enabled.

 If DWARF frame unwinders are not supported for a particular target
 architecture, then enabling this flag does not cause them to be used.
+
+@kindex maint set worker-threads
+@kindex maint show worker-threads
+@item maint set worker-threads
+@item maint show worker-threads
+Control the number of worker threads that may be used by @value{GDBN}.
+On capable hosts, @value{GDBN} may use multiple threads to speed up
+certain CPU-intensive operations, such as demangling symbol names.
+While the number of threads used by @value{GDBN} may vary, this
+command can be used to set an upper bound on this number.  The default
+is @code{unlimited}, which lets @value{GDBN} choose a reasonable
+number.  Note that this only controls worker threads started by
+@value{GDBN} itself; libraries used by @value{GDBN} may start threads
+of their own.
+
@kindex maint set profile
@kindex maint show profile
@cindex profiling GDB
--- a/gdb/event-top.c
+++ b/gdb/event-top.c
@@ -40,6 +40,7 @@
 #include "gdbsupport/buffer.h"
 #include "ser-event.h"
 #include "gdb_select.h"
+#include "gdbsupport/gdb-sigmask.h"

 /* readline include files.  */
 #include "readline/readline.h"
@@ -847,6 +848,45 @@ gdb_readline_no_editing_callback (gdb_client_data client_data)
 }


+/* See event-top.h.  */
+
+thread_local void (*thread_local_segv_handler) (int);
+
+static void handle_sigsegv (int sig);
+
+/* Install the SIGSEGV handler.  */
+static void
+install_handle_sigsegv ()
+{
+#if defined (HAVE_SIGACTION)
+  struct sigaction sa;
+  sa.sa_handler = handle_sigsegv;
+  sigemptyset (&sa.sa_mask);
+#ifdef HAVE_SIGALTSTACK
+  sa.sa_flags = SA_ONSTACK;
+#else
+  sa.sa_flags = 0;
+#endif
+  sigaction (SIGSEGV, &sa, nullptr);
+#else
+  signal (SIGSEGV, handle_sigsegv);
+#endif
+}
+
+/* Handler for SIGSEGV.  */
+
+static void
+handle_sigsegv (int sig)
+{
+  install_handle_sigsegv ();
+
+  if (thread_local_segv_handler == nullptr)
+    abort ();
+  thread_local_segv_handler (sig);
+}
+
+
+
 /* The serial event associated with the QUIT flag.  set_quit_flag sets
   this, and check_quit_flag clears it.  Used by interruptible_select
   to be able to do interruptible I/O with no race with the SIGINT
@@ -914,6 +954,8 @@ async_init_signals (void)
  sigtstp_token =
    create_async_signal_handler (async_sigtstp_handler, NULL);
 #endif
+
+  install_handle_sigsegv ();
 }

 /* See defs.h.  */
@@ -1127,7 +1169,7 @@ async_sigtstp_handler (gdb_client_data arg)
    sigset_t zero;

    sigemptyset (&zero);
-    sigprocmask (SIG_SETMASK, &zero, 0);
+    gdb_sigmask (SIG_SETMASK, &zero, 0);
  }
 #elif HAVE_SIGSETMASK
  sigsetmask (0);
--- a/gdb/event-top.h
+++ b/gdb/event-top.h
@@ -70,4 +70,10 @@ extern void gdb_rl_callback_handler_install (const char *prompt);
   currently installed.  */
 extern void gdb_rl_callback_handler_reinstall (void);

+/* The SIGSEGV handler for this thread, or NULL if there is none.  GDB
+   always installs a global SIGSEGV handler, and then lets threads
+   indicate their interest in handling the signal by setting this
+   thread-local variable.  */
+extern thread_local void (*thread_local_segv_handler) (int);
+
 #endif
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,22 @@
+2019-10-19  Tom Tromey  <tom@tromey.com>
+
+	* configure, config.in: Rebuild.
+
+2019-10-19  Tom Tromey  <tom@tromey.com>
+
+	* remote-utils.c (block_unblock_async_io): Use gdb_sigmask.
+	* linux-low.c (linux_wait_for_event_filtered, linux_async): Use
+	gdb_sigmask.
+	* configure, config.in: Rebuild.
+
+2019-10-19  Tom Tromey  <tom@tromey.com>
+
+	* Makefile.in (PTHREAD_CFLAGS, PTHREAD_LIBS): New variables.
+	(INTERNAL_CFLAGS_BASE): Use PTHREAD_CFLAGS.
+	(GDBSERVER_LIBS): Use PTHREAD_LIBS.
+	* acinclude.m4: Include ax_pthread.m4.
+	* config.in, configure: Rebuild.
+
 2019-11-06  Christian Biesinger  <cbiesinger@google.com>

 	* linux-tdep.c (linux_info_proc): Use strtok_r instead of strtok.
--- a/gdb/gdbserver/Makefile.in
+++ b/gdb/gdbserver/Makefile.in
@@ -139,9 +139,12 @@ CFLAGS = @CFLAGS@
 CXXFLAGS = @CXXFLAGS@
 CPPFLAGS = @CPPFLAGS@

+PTHREAD_CFLAGS = @PTHREAD_CFLAGS@
+PTHREAD_LIBS = @PTHREAD_LIBS@
+
 # INTERNAL_CFLAGS is the aggregate of all other *CFLAGS macros.
 INTERNAL_CFLAGS_BASE = ${CXXFLAGS} ${GLOBAL_CFLAGS} \
-	${PROFILE_CFLAGS} ${INCLUDE_CFLAGS} ${CPPFLAGS}
+	${PROFILE_CFLAGS} ${INCLUDE_CFLAGS} ${CPPFLAGS} $(PTHREAD_CFLAGS)
 INTERNAL_WARN_CFLAGS = ${INTERNAL_CFLAGS_BASE} $(WARN_CFLAGS)
 INTERNAL_CFLAGS = ${INTERNAL_WARN_CFLAGS} $(WERROR_CFLAGS) -DGDBSERVER

@@ -303,7 +306,7 @@ GDBREPLAY_OBS = \
 	utils.o \
 	version.o

-GDBSERVER_LIBS = @GDBSERVER_LIBS@
+GDBSERVER_LIBS = @GDBSERVER_LIBS@ $(PTHREAD_LIBS)
 XM_CLIBS = @LIBS@
 CDEPS = $(srcdir)/proc-service.list

--- a/gdb/gdbserver/acinclude.m4
+++ b/gdb/gdbserver/acinclude.m4
@@ -31,6 +31,8 @@ m4_include(../ax_cxx_compile_stdcxx.m4)
 dnl For GDB_AC_SELFTEST.
 m4_include(../selftest.m4)

+m4_include([../../config/ax_pthread.m4])
+
 dnl Check for existence of a type $1 in libthread_db.h
 dnl Based on BFD_HAVE_SYS_PROCFS_TYPE in bfd/bfd.m4.

--- a/gdb/gdbserver/config.in
+++ b/gdb/gdbserver/config.in
@@ -5,6 +5,9 @@
   */
 #undef CRAY_STACKSEG_END

+/* Define to 1 if std::thread works. */
+#undef CXX_STD_THREAD
+
 /* Define to 1 if using `alloca.c'. */
 #undef C_ALLOCA

@@ -189,6 +192,15 @@
 /* Define if <thread_db.h> has psaddr_t. */
 #undef HAVE_PSADDR_T

+/* Have PTHREAD_PRIO_INHERIT. */
+#undef HAVE_PTHREAD_PRIO_INHERIT
+
+/* Define to 1 if you have the `pthread_setname_np' function. */
+#undef HAVE_PTHREAD_SETNAME_NP
+
+/* Define to 1 if you have the `pthread_sigmask' function. */
+#undef HAVE_PTHREAD_SIGMASK
+
 /* Define if the target supports PTRACE_GETFPXREGS for extended register
   access. */
 #undef HAVE_PTRACE_GETFPXREGS
@@ -337,6 +349,10 @@
 /* Additional package description */
 #undef PKGVERSION

+/* Define to necessary symbol if this constant uses a non-standard name on
+   your system. */
+#undef PTHREAD_CREATE_JOINABLE
+
 /* Define to the type of arg 1 for ptrace. */
 #undef PTRACE_TYPE_ARG1

--- a/gdb/gdbserver/configure
+++ b/gdb/gdbserver/configure
@@ -636,6 +636,11 @@ WERROR_CFLAGS
 WARN_CFLAGS
 ustinc
 ustlibs
+PTHREAD_CFLAGS
+PTHREAD_LIBS
+PTHREAD_CC
+ax_pthread_config
+SED
 ALLOCA
 CCDEPMODE
 CONFIG_SRC_SUBDIR
@@ -1967,6 +1972,119 @@ $as_echo "$ac_res" >&6; }

 } # ac_fn_c_check_decl

+# ac_fn_cxx_try_link LINENO
+# -------------------------
+# Try to link conftest.$ac_ext, and return whether this succeeded.
+ac_fn_cxx_try_link ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  rm -f conftest.$ac_objext conftest$ac_exeext
+  if { { ac_try="$ac_link"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval ac_try_echo="\"\$as_me:${as_lineno-$LINENO}: $ac_try_echo\""
+$as_echo "$ac_try_echo"; } >&5
+  (eval "$ac_link") 2>conftest.err
+  ac_status=$?
+  if test -s conftest.err; then
+    grep -v '^ *+' conftest.err >conftest.er1
+    cat conftest.er1 >&5
+    mv -f conftest.er1 conftest.err
+  fi
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; } && {
+	 test -z "$ac_cxx_werror_flag" ||
+	 test ! -s conftest.err
+       } && test -s conftest$ac_exeext && {
+	 test "$cross_compiling" = yes ||
+	 test -x conftest$ac_exeext
+       }; then :
+  ac_retval=0
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+	ac_retval=1
+fi
+  # Delete the IPA/IPO (Inter Procedural Analysis/Optimization) information
+  # created by the PGI compiler (conftest_ipa8_conftest.oo), as it would
+  # interfere with the next link command; also delete a directory that is
+  # left behind by Apple's compiler.  We do this before executing the actions.
+  rm -rf conftest.dSYM conftest_ipa8_conftest.oo
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+  as_fn_set_status $ac_retval
+
+} # ac_fn_cxx_try_link
+
+# ac_fn_cxx_check_func LINENO FUNC VAR
+# ------------------------------------
+# Tests whether FUNC exists, setting the cache variable VAR accordingly
+ac_fn_cxx_check_func ()
+{
+  as_lineno=${as_lineno-"$1"} as_lineno_stack=as_lineno_stack=$as_lineno_stack
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for $2" >&5
+$as_echo_n "checking for $2... " >&6; }
+if eval \${$3+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+/* Define $2 to an innocuous variant, in case <limits.h> declares $2.
+   For example, HP-UX 11i <limits.h> declares gettimeofday.  */
+#define $2 innocuous_$2
+
+/* System header to define __stub macros and hopefully few prototypes,
+    which can conflict with char $2 (); below.
+    Prefer <limits.h> to <assert.h> if __STDC__ is defined, since
+    <limits.h> exists even on freestanding compilers.  */
+
+#ifdef __STDC__
+# include <limits.h>
+#else
+# include <assert.h>
+#endif
+
+#undef $2
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char $2 ();
+/* The GNU C library defines this for functions which it implements
+    to always fail with ENOSYS.  Some functions are actually named
+    something starting with __ and the normal name is an alias.  */
+#if defined __stub_$2 || defined __stub___$2
+choke me
+#endif
+
+int
+main ()
+{
+return $2 ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+  eval "$3=yes"
+else
+  eval "$3=no"
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+fi
+eval ac_res=\$$3
+	       { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_res" >&5
+$as_echo "$ac_res" >&6; }
+  eval $as_lineno_stack; ${as_lineno_stack:+:} unset as_lineno
+
+} # ac_fn_cxx_check_func
+
 # ac_fn_c_compute_int LINENO EXPR VAR INCLUDES
 # --------------------------------------------
 # Tries to find the compile-time value of EXPR in a program that includes
@@ -6472,6 +6590,75 @@ _ACEOF

 fi

+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for a sed that does not truncate output" >&5
+$as_echo_n "checking for a sed that does not truncate output... " >&6; }
+if ${ac_cv_path_SED+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+            ac_script=s/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa/bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb/
+     for ac_i in 1 2 3 4 5 6 7; do
+       ac_script="$ac_script$as_nl$ac_script"
+     done
+     echo "$ac_script" 2>/dev/null | sed 99q >conftest.sed
+     { ac_script=; unset ac_script;}
+     if test -z "$SED"; then
+  ac_path_SED_found=false
+  # Loop through the user's path and test for each of PROGNAME-LIST
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_prog in sed gsed; do
+    for ac_exec_ext in '' $ac_executable_extensions; do
+      ac_path_SED="$as_dir/$ac_prog$ac_exec_ext"
+      as_fn_executable_p "$ac_path_SED" || continue
+# Check for GNU ac_path_SED and select it if it is found.
+  # Check for GNU $ac_path_SED
+case `"$ac_path_SED" --version 2>&1` in
+*GNU*)
+  ac_cv_path_SED="$ac_path_SED" ac_path_SED_found=:;;
+*)
+  ac_count=0
+  $as_echo_n 0123456789 >"conftest.in"
+  while :
+  do
+    cat "conftest.in" "conftest.in" >"conftest.tmp"
+    mv "conftest.tmp" "conftest.in"
+    cp "conftest.in" "conftest.nl"
+    $as_echo '' >> "conftest.nl"
+    "$ac_path_SED" -f conftest.sed < "conftest.nl" >"conftest.out" 2>/dev/null || break
+    diff "conftest.out" "conftest.nl" >/dev/null 2>&1 || break
+    as_fn_arith $ac_count + 1 && ac_count=$as_val
+    if test $ac_count -gt ${ac_path_SED_max-0}; then
+      # Best one so far, save it but keep looking for a better one
+      ac_cv_path_SED="$ac_path_SED"
+      ac_path_SED_max=$ac_count
+    fi
+    # 10*(2^10) chars as input seems more than enough
+    test $ac_count -gt 10 && break
+  done
+  rm -f conftest.in conftest.tmp conftest.nl conftest.out;;
+esac
+
+      $ac_path_SED_found && break 3
+    done
+  done
+  done
+IFS=$as_save_IFS
+  if test -z "$ac_cv_path_SED"; then
+    as_fn_error $? "no acceptable sed could be found in \$PATH" "$LINENO" 5
+  fi
+else
+  ac_cv_path_SED=$SED
+fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_path_SED" >&5
+$as_echo "$ac_cv_path_SED" >&6; }
+ SED="$ac_cv_path_SED"
+  rm -f conftest.sed
+

  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for ANSI C header files" >&5
 $as_echo_n "checking for ANSI C header files... " >&6; }
@@ -6857,6 +7044,715 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF


+  # Check for std::thread.  This does not work on some platforms, like
+  # mingw and DJGPP.
+  ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+
+
+
+
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+ax_pthread_ok=no
+
+# We used to check for pthread.h first, but this fails if pthread.h
+# requires special compiler flags (e.g. on Tru64 or Sequent).
+# It gets checked for in the link test anyway.
+
+# First of all, check if the user has set any of the PTHREAD_LIBS,
+# etcetera environment variables, and if threads linking works using
+# them:
+if test "x$PTHREAD_CFLAGS$PTHREAD_LIBS" != "x"; then
+        ax_pthread_save_CC="$CC"
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        if test "x$PTHREAD_CC" != "x"; then :
+  CC="$PTHREAD_CC"
+fi
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS" >&5
+$as_echo_n "checking for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS... " >&6; }
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char pthread_join ();
+int
+main ()
+{
+return pthread_join ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_pthread_ok=yes
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_ok" >&5
+$as_echo "$ax_pthread_ok" >&6; }
+        if test "x$ax_pthread_ok" = "xno"; then
+                PTHREAD_LIBS=""
+                PTHREAD_CFLAGS=""
+        fi
+        CC="$ax_pthread_save_CC"
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+fi
+
+# We must check for the threads library under a number of different
+# names; the ordering is very important because some systems
+# (e.g. DEC) have both -lpthread and -lpthreads, where one of the
+# libraries is broken (non-POSIX).
+
+# Create a list of thread flags to try.  Items starting with a "-" are
+# C compiler flags, and other items are library names, except for "none"
+# which indicates that we try without any flags at all, and "pthread-config"
+# which is a program returning the flags for the Pth emulation library.
+
+ax_pthread_flags="pthreads none -Kthread -pthread -pthreads -mthreads pthread --thread-safe -mt pthread-config"
+
+# The ordering *is* (sometimes) important.  Some notes on the
+# individual items follow:
+
+# pthreads: AIX (must check this before -lpthread)
+# none: in case threads are in libc; should be tried before -Kthread and
+#       other compiler flags to prevent continual compiler warnings
+# -Kthread: Sequent (threads in libc, but -Kthread needed for pthread.h)
+# -pthread: Linux/gcc (kernel threads), BSD/gcc (userland threads), Tru64
+#           (Note: HP C rejects this with "bad form for `-t' option")
+# -pthreads: Solaris/gcc (Note: HP C also rejects)
+# -mt: Sun Workshop C (may only link SunOS threads [-lthread], but it
+#      doesn't hurt to check since this sometimes defines pthreads and
+#      -D_REENTRANT too), HP C (must be checked before -lpthread, which
+#      is present but should not be used directly; and before -mthreads,
+#      because the compiler interprets this as "-mt" + "-hreads")
+# -mthreads: Mingw32/gcc, Lynx/gcc
+# pthread: Linux, etcetera
+# --thread-safe: KAI C++
+# pthread-config: use pthread-config program (for GNU Pth library)
+
+case $host_os in
+
+        freebsd*)
+
+        # -kthread: FreeBSD kernel threads (preferred to -pthread since SMP-able)
+        # lthread: LinuxThreads port on FreeBSD (also preferred to -pthread)
+
+        ax_pthread_flags="-kthread lthread $ax_pthread_flags"
+        ;;
+
+        hpux*)
+
+        # From the cc(1) man page: "[-mt] Sets various -D flags to enable
+        # multi-threading and also sets -lpthread."
+
+        ax_pthread_flags="-mt -pthread pthread $ax_pthread_flags"
+        ;;
+
+        openedition*)
+
+        # IBM z/OS requires a feature-test macro to be defined in order to
+        # enable POSIX threads at all, so give the user a hint if this is
+        # not set. (We don't define these ourselves, as they can affect
+        # other portions of the system API in unpredictable ways.)
+
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+#            if !defined(_OPEN_THREADS) && !defined(_UNIX03_THREADS)
+             AX_PTHREAD_ZOS_MISSING
+#            endif
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "AX_PTHREAD_ZOS_MISSING" >/dev/null 2>&1; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support." >&5
+$as_echo "$as_me: WARNING: IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support." >&2;}
+fi
+rm -f conftest*
+
+        ;;
+
+        solaris*)
+
+        # On Solaris (at least, for some versions), libc contains stubbed
+        # (non-functional) versions of the pthreads routines, so link-based
+        # tests will erroneously succeed. (N.B.: The stubs are missing
+        # pthread_cleanup_push, or rather a function called by this macro,
+        # so we could check for that, but who knows whether they'll stub
+        # that too in a future libc.)  So we'll check first for the
+        # standard Solaris way of linking pthreads (-mt -lpthread).
+
+        ax_pthread_flags="-mt,pthread pthread $ax_pthread_flags"
+        ;;
+esac
+
+# GCC generally uses -pthread, or -pthreads on some platforms (e.g. SPARC)
+
+if test "x$GCC" = "xyes"; then :
+  ax_pthread_flags="-pthread -pthreads $ax_pthread_flags"
+fi
+
+# The presence of a feature test macro requesting re-entrant function
+# definitions is, on some systems, a strong hint that pthreads support is
+# correctly enabled
+
+case $host_os in
+        darwin* | hpux* | linux* | osf* | solaris*)
+        ax_pthread_check_macro="_REENTRANT"
+        ;;
+
+        aix*)
+        ax_pthread_check_macro="_THREAD_SAFE"
+        ;;
+
+        *)
+        ax_pthread_check_macro="--"
+        ;;
+esac
+if test "x$ax_pthread_check_macro" = "x--"; then :
+  ax_pthread_check_cond=0
+else
+  ax_pthread_check_cond="!defined($ax_pthread_check_macro)"
+fi
+
+# Are we compiling with Clang?
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether $CC is Clang" >&5
+$as_echo_n "checking whether $CC is Clang... " >&6; }
+if ${ax_cv_PTHREAD_CLANG+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_CLANG=no
+     # Note that Autoconf sets GCC=yes for Clang as well as GCC
+     if test "x$GCC" = "xyes"; then
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+/* Note: Clang 2.7 lacks __clang_[a-z]+__ */
+#            if defined(__clang__) && defined(__llvm__)
+             AX_PTHREAD_CC_IS_CLANG
+#            endif
+
+_ACEOF
+if (eval "$ac_cpp conftest.$ac_ext") 2>&5 |
+  $EGREP "AX_PTHREAD_CC_IS_CLANG" >/dev/null 2>&1; then :
+  ax_cv_PTHREAD_CLANG=yes
+fi
+rm -f conftest*
+
+     fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_CLANG" >&5
+$as_echo "$ax_cv_PTHREAD_CLANG" >&6; }
+ax_pthread_clang="$ax_cv_PTHREAD_CLANG"
+
+ax_pthread_clang_warning=no
+
+# Clang needs special handling, because older versions handle the -pthread
+# option in a rather... idiosyncratic way
+
+if test "x$ax_pthread_clang" = "xyes"; then
+
+        # Clang takes -pthread; it has never supported any other flag
+
+        # (Note 1: This will need to be revisited if a system that Clang
+        # supports has POSIX threads in a separate library.  This tends not
+        # to be the way of modern systems, but it's conceivable.)
+
+        # (Note 2: On some systems, notably Darwin, -pthread is not needed
+        # to get POSIX threads support; the API is always present and
+        # active.  We could reasonably leave PTHREAD_CFLAGS empty.  But
+        # -pthread does define _REENTRANT, and while the Darwin headers
+        # ignore this macro, third-party headers might not.)
+
+        PTHREAD_CFLAGS="-pthread"
+        PTHREAD_LIBS=
+
+        ax_pthread_ok=yes
+
+        # However, older versions of Clang make a point of warning the user
+        # that, in an invocation where only linking and no compilation is
+        # taking place, the -pthread option has no effect ("argument unused
+        # during compilation").  They expect -pthread to be passed in only
+        # when source code is being compiled.
+        #
+        # Problem is, this is at odds with the way Automake and most other
+        # C build frameworks function, which is that the same flags used in
+        # compilation (CFLAGS) are also used in linking.  Many systems
+        # supported by AX_PTHREAD require exactly this for POSIX threads
+        # support, and in fact it is often not straightforward to specify a
+        # flag that is used only in the compilation phase and not in
+        # linking.  Such a scenario is extremely rare in practice.
+        #
+        # Even though use of the -pthread flag in linking would only print
+        # a warning, this can be a nuisance for well-run software projects
+        # that build with -Werror.  So if the active version of Clang has
+        # this misfeature, we search for an option to squash it.
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether Clang needs flag to prevent \"argument unused\" warning when linking with -pthread" >&5
+$as_echo_n "checking whether Clang needs flag to prevent \"argument unused\" warning when linking with -pthread... " >&6; }
+if ${ax_cv_PTHREAD_CLANG_NO_WARN_FLAG+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_CLANG_NO_WARN_FLAG=unknown
+             # Create an alternate version of $ac_link that compiles and
+             # links in two steps (.c -> .o, .o -> exe) instead of one
+             # (.c -> exe), because the warning occurs only in the second
+             # step
+             ax_pthread_save_ac_link="$ac_link"
+             ax_pthread_sed='s/conftest\.\$ac_ext/conftest.$ac_objext/g'
+             ax_pthread_link_step=`$as_echo "$ac_link" | sed "$ax_pthread_sed"`
+             ax_pthread_2step_ac_link="($ac_compile) && (echo ==== >&5) && ($ax_pthread_link_step)"
+             ax_pthread_save_CFLAGS="$CFLAGS"
+             for ax_pthread_try in '' -Qunused-arguments -Wno-unused-command-line-argument unknown; do
+                if test "x$ax_pthread_try" = "xunknown"; then :
+  break
+fi
+                CFLAGS="-Werror -Wunknown-warning-option $ax_pthread_try -pthread $ax_pthread_save_CFLAGS"
+                ac_link="$ax_pthread_save_ac_link"
+                cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+int main(void){return 0;}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_link="$ax_pthread_2step_ac_link"
+                     cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+int main(void){return 0;}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  break
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+             done
+             ac_link="$ax_pthread_save_ac_link"
+             CFLAGS="$ax_pthread_save_CFLAGS"
+             if test "x$ax_pthread_try" = "x"; then :
+  ax_pthread_try=no
+fi
+             ax_cv_PTHREAD_CLANG_NO_WARN_FLAG="$ax_pthread_try"
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" >&5
+$as_echo "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" >&6; }
+
+        case "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" in
+                no | unknown) ;;
+                *) PTHREAD_CFLAGS="$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG $PTHREAD_CFLAGS" ;;
+        esac
+
+fi # $ax_pthread_clang = yes
+
+if test "x$ax_pthread_ok" = "xno"; then
+for ax_pthread_try_flag in $ax_pthread_flags; do
+
+        case $ax_pthread_try_flag in
+                none)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work without any flags" >&5
+$as_echo_n "checking whether pthreads work without any flags... " >&6; }
+                ;;
+
+                -mt,pthread)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work with -mt -lpthread" >&5
+$as_echo_n "checking whether pthreads work with -mt -lpthread... " >&6; }
+                PTHREAD_CFLAGS="-mt"
+                PTHREAD_LIBS="-lpthread"
+                ;;
+
+                -*)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether pthreads work with $ax_pthread_try_flag" >&5
+$as_echo_n "checking whether pthreads work with $ax_pthread_try_flag... " >&6; }
+                PTHREAD_CFLAGS="$ax_pthread_try_flag"
+                ;;
+
+                pthread-config)
+                # Extract the first word of "pthread-config", so it can be a program name with args.
+set dummy pthread-config; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_prog_ax_pthread_config+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$ax_pthread_config"; then
+  ac_cv_prog_ax_pthread_config="$ax_pthread_config" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_ax_pthread_config="yes"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  test -z "$ac_cv_prog_ax_pthread_config" && ac_cv_prog_ax_pthread_config="no"
+fi
+fi
+ax_pthread_config=$ac_cv_prog_ax_pthread_config
+if test -n "$ax_pthread_config"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_config" >&5
+$as_echo "$ax_pthread_config" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+                if test "x$ax_pthread_config" = "xno"; then :
+  continue
+fi
+                PTHREAD_CFLAGS="`pthread-config --cflags`"
+                PTHREAD_LIBS="`pthread-config --ldflags` `pthread-config --libs`"
+                ;;
+
+                *)
+                { $as_echo "$as_me:${as_lineno-$LINENO}: checking for the pthreads library -l$ax_pthread_try_flag" >&5
+$as_echo_n "checking for the pthreads library -l$ax_pthread_try_flag... " >&6; }
+                PTHREAD_LIBS="-l$ax_pthread_try_flag"
+                ;;
+        esac
+
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Check for various functions.  We must include pthread.h,
+        # since some functions may be macros.  (On the Sequent, we
+        # need a special flag -Kthread to make this header compile.)
+        # We check for pthread_join because it is in -lpthread on IRIX
+        # while pthread_create is in libc.  We check for pthread_attr_init
+        # due to DEC craziness with -lpthreads.  We check for
+        # pthread_cleanup_push because it is one of the few pthread
+        # functions on Solaris that doesn't have a non-functional libc stub.
+        # We try pthread_create on general principles.
+
+        cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+#                       if $ax_pthread_check_cond
+#                        error "$ax_pthread_check_macro must be defined"
+#                       endif
+                        static void routine(void *a) { a = 0; }
+                        static void *start_routine(void *a) { return a; }
+int
+main ()
+{
+pthread_t th; pthread_attr_t attr;
+                        pthread_create(&th, 0, start_routine, 0);
+                        pthread_join(th, 0);
+                        pthread_attr_init(&attr);
+                        pthread_cleanup_push(routine, 0);
+                        pthread_cleanup_pop(0) /* ; */
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_pthread_ok=yes
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_pthread_ok" >&5
+$as_echo "$ax_pthread_ok" >&6; }
+        if test "x$ax_pthread_ok" = "xyes"; then :
+  break
+fi
+
+        PTHREAD_LIBS=""
+        PTHREAD_CFLAGS=""
+done
+fi
+
+# Various other checks:
+if test "x$ax_pthread_ok" = "xyes"; then
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Detect AIX lossage: JOINABLE attribute is called UNDETACHED.
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for joinable pthread attribute" >&5
+$as_echo_n "checking for joinable pthread attribute... " >&6; }
+if ${ax_cv_PTHREAD_JOINABLE_ATTR+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_JOINABLE_ATTR=unknown
+             for ax_pthread_attr in PTHREAD_CREATE_JOINABLE PTHREAD_CREATE_UNDETACHED; do
+                 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main ()
+{
+int attr = $ax_pthread_attr; return attr /* ; */
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_cv_PTHREAD_JOINABLE_ATTR=$ax_pthread_attr; break
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+             done
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_JOINABLE_ATTR" >&5
+$as_echo "$ax_cv_PTHREAD_JOINABLE_ATTR" >&6; }
+        if test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xunknown" && \
+               test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xPTHREAD_CREATE_JOINABLE" && \
+               test "x$ax_pthread_joinable_attr_defined" != "xyes"; then :
+
+cat >>confdefs.h <<_ACEOF
+#define PTHREAD_CREATE_JOINABLE $ax_cv_PTHREAD_JOINABLE_ATTR
+_ACEOF
+
+               ax_pthread_joinable_attr_defined=yes
+
+fi
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether more special flags are required for pthreads" >&5
+$as_echo_n "checking whether more special flags are required for pthreads... " >&6; }
+if ${ax_cv_PTHREAD_SPECIAL_FLAGS+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ax_cv_PTHREAD_SPECIAL_FLAGS=no
+             case $host_os in
+             solaris*)
+             ax_cv_PTHREAD_SPECIAL_FLAGS="-D_POSIX_PTHREAD_SEMANTICS"
+             ;;
+             esac
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_SPECIAL_FLAGS" >&5
+$as_echo "$ax_cv_PTHREAD_SPECIAL_FLAGS" >&6; }
+        if test "x$ax_cv_PTHREAD_SPECIAL_FLAGS" != "xno" && \
+               test "x$ax_pthread_special_flags_added" != "xyes"; then :
+  PTHREAD_CFLAGS="$ax_cv_PTHREAD_SPECIAL_FLAGS $PTHREAD_CFLAGS"
+               ax_pthread_special_flags_added=yes
+fi
+
+        { $as_echo "$as_me:${as_lineno-$LINENO}: checking for PTHREAD_PRIO_INHERIT" >&5
+$as_echo_n "checking for PTHREAD_PRIO_INHERIT... " >&6; }
+if ${ax_cv_PTHREAD_PRIO_INHERIT+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <pthread.h>
+int
+main ()
+{
+int i = PTHREAD_PRIO_INHERIT;
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ax_cv_PTHREAD_PRIO_INHERIT=yes
+else
+  ax_cv_PTHREAD_PRIO_INHERIT=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_PTHREAD_PRIO_INHERIT" >&5
+$as_echo "$ax_cv_PTHREAD_PRIO_INHERIT" >&6; }
+        if test "x$ax_cv_PTHREAD_PRIO_INHERIT" = "xyes" && \
+               test "x$ax_pthread_prio_inherit_defined" != "xyes"; then :
+
+$as_echo "#define HAVE_PTHREAD_PRIO_INHERIT 1" >>confdefs.h
+
+               ax_pthread_prio_inherit_defined=yes
+
+fi
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        # More AIX lossage: compile with *_r variant
+        if test "x$GCC" != "xyes"; then
+            case $host_os in
+                aix*)
+                case "x/$CC" in #(
+  x*/c89|x*/c89_128|x*/c99|x*/c99_128|x*/cc|x*/cc128|x*/xlc|x*/xlc_v6|x*/xlc128|x*/xlc128_v6) :
+    #handle absolute path differently from PATH based program lookup
+                     case "x$CC" in #(
+  x/*) :
+    if as_fn_executable_p ${CC}_r; then :
+  PTHREAD_CC="${CC}_r"
+fi ;; #(
+  *) :
+    for ac_prog in ${CC}_r
+do
+  # Extract the first word of "$ac_prog", so it can be a program name with args.
+set dummy $ac_prog; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_prog_PTHREAD_CC+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if test -n "$PTHREAD_CC"; then
+  ac_cv_prog_PTHREAD_CC="$PTHREAD_CC" # Let the user override the test.
+else
+as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_prog_PTHREAD_CC="$ac_prog"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+fi
+fi
+PTHREAD_CC=$ac_cv_prog_PTHREAD_CC
+if test -n "$PTHREAD_CC"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $PTHREAD_CC" >&5
+$as_echo "$PTHREAD_CC" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+  test -n "$PTHREAD_CC" && break
+done
+test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+ ;;
+esac ;; #(
+  *) :
+     ;;
+esac
+                ;;
+            esac
+        fi
+fi
+
+test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+
+
+
+
+
+# Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND:
+if test "x$ax_pthread_ok" = "xyes"; then
+        threads=yes
+        :
+else
+        ax_pthread_ok=no
+        threads=no
+fi
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+
+  if test "$threads" = "yes"; then
+    save_LIBS="$LIBS"
+    LIBS="$PTHREAD_LIBS $LIBS"
+    save_CXXFLAGS="$CXXFLAGS"
+    CXXFLAGS="$PTHREAD_CFLAGS $save_CFLAGS"
+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for std::thread" >&5
+$as_echo_n "checking for std::thread... " >&6; }
+if ${gdb_cv_cxx_std_thread+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <thread>
+      void callback() { }
+int
+main ()
+{
+std::thread t(callback);
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  gdb_cv_cxx_std_thread=yes
+else
+  gdb_cv_cxx_std_thread=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gdb_cv_cxx_std_thread" >&5
+$as_echo "$gdb_cv_cxx_std_thread" >&6; }
+
+    # This check must be here, while LIBS includes any necessary
+    # threading library.
+    for ac_func in pthread_sigmask pthread_setname_np
+do :
+  as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
+ac_fn_cxx_check_func "$LINENO" "$ac_func" "$as_ac_var"
+if eval test \"x\$"$as_ac_var"\" = x"yes"; then :
+  cat >>confdefs.h <<_ACEOF
+#define `$as_echo "HAVE_$ac_func" | $as_tr_cpp` 1
+_ACEOF
+
+fi
+done
+
+
+    LIBS="$save_LIBS"
+    CXXFLAGS="$save_CXXFLAGS"
+  fi
+  if test $gdb_cv_cxx_std_thread = yes; then
+
+$as_echo "#define CXX_STD_THREAD 1" >>confdefs.h
+
+  fi
+  ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+
    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sigsetjmp" >&5
 $as_echo_n "checking for sigsetjmp... " >&6; }
 if ${gdb_cv_func_sigsetjmp+:} false; then :
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -50,6 +50,7 @@
 #include "gdbsupport/common-inferior.h"
 #include "nat/fork-inferior.h"
 #include "gdbsupport/environ.h"
+#include "gdbsupport/gdb-sigmask.h"
 #include "gdbsupport/scoped_restore.h"
 #ifndef ELFMAG0
 /* Don't include <linux/elf.h> here.  If it got included by gdb_proc_service.h
@@ -2689,7 +2690,7 @@ linux_wait_for_event_filtered (ptid_t wait_ptid, ptid_t filter_ptid,
  /* Make sure SIGCHLD is blocked until the sigsuspend below.  Block
     all signals while here.  */
  sigfillset (&block_mask);
-  sigprocmask (SIG_BLOCK, &block_mask, &prev_mask);
+  gdb_sigmask (SIG_BLOCK, &block_mask, &prev_mask);

  /* Always pull all events out of the kernel.  We'll randomly select
     an event LWP out of all that have events, to prevent
@@ -2775,7 +2776,7 @@ linux_wait_for_event_filtered (ptid_t wait_ptid, ptid_t filter_ptid,
 	{
 	  if (debug_threads)
 	    debug_printf ("LLW: exit (no unwaited-for LWP)\n");
-	  sigprocmask (SIG_SETMASK, &prev_mask, NULL);
+	  gdb_sigmask (SIG_SETMASK, &prev_mask, NULL);
 	  return -1;
 	}

@@ -2785,7 +2786,7 @@ linux_wait_for_event_filtered (ptid_t wait_ptid, ptid_t filter_ptid,
 	  if (debug_threads)
 	    debug_printf ("WNOHANG set, no event found\n");

-	  sigprocmask (SIG_SETMASK, &prev_mask, NULL);
+	  gdb_sigmask (SIG_SETMASK, &prev_mask, NULL);
 	  return 0;
 	}

@@ -2794,11 +2795,11 @@ linux_wait_for_event_filtered (ptid_t wait_ptid, ptid_t filter_ptid,
 	debug_printf ("sigsuspend'ing\n");

      sigsuspend (&prev_mask);
-      sigprocmask (SIG_SETMASK, &prev_mask, NULL);
+      gdb_sigmask (SIG_SETMASK, &prev_mask, NULL);
      goto retry;
    }

-  sigprocmask (SIG_SETMASK, &prev_mask, NULL);
+  gdb_sigmask (SIG_SETMASK, &prev_mask, NULL);

  current_thread = event_thread;

@@ -6215,7 +6216,7 @@ linux_async (int enable)
      sigemptyset (&mask);
      sigaddset (&mask, SIGCHLD);

-      sigprocmask (SIG_BLOCK, &mask, NULL);
+      gdb_sigmask (SIG_BLOCK, &mask, NULL);

      if (enable)
 	{
@@ -6223,7 +6224,7 @@ linux_async (int enable)
 	    {
 	      linux_event_pipe[0] = -1;
 	      linux_event_pipe[1] = -1;
-	      sigprocmask (SIG_UNBLOCK, &mask, NULL);
+	      gdb_sigmask (SIG_UNBLOCK, &mask, NULL);

 	      warning ("creating event pipe failed.");
 	      return previous;
@@ -6249,7 +6250,7 @@ linux_async (int enable)
 	  linux_event_pipe[1] = -1;
 	}

-      sigprocmask (SIG_UNBLOCK, &mask, NULL);
+      gdb_sigmask (SIG_UNBLOCK, &mask, NULL);
    }

  return previous;
--- a/gdb/gdbserver/remote-utils.c
+++ b/gdb/gdbserver/remote-utils.c
@@ -28,6 +28,7 @@
 #include "gdbsupport/rsp-low.h"
 #include "gdbsupport/netstuff.h"
 #include "gdbsupport/filestuff.h"
+#include "gdbsupport/gdb-sigmask.h"
 #include <ctype.h>
 #if HAVE_SYS_IOCTL_H
 #include <sys/ioctl.h>
@@ -807,7 +808,7 @@ block_unblock_async_io (int block)

  sigemptyset (&sigio_set);
  sigaddset (&sigio_set, SIGIO);
-  sigprocmask (block ? SIG_BLOCK : SIG_UNBLOCK, &sigio_set, NULL);
+  gdb_sigmask (block ? SIG_BLOCK : SIG_UNBLOCK, &sigio_set, NULL);
 #endif
 }

--- a/gdb/gdbsupport/alt-stack.h
+++ b/gdb/gdbsupport/alt-stack.h
@@ -0,0 +1,70 @@
+/* Temporarily install an alternate signal stack
+
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GDBSUPPORT_ALT_STACK_H
+#define GDBSUPPORT_ALT_STACK_H
+
+#include <signal.h>
+
+namespace gdb
+{
+
+/* Try to set up an alternate signal stack for SIGSEGV handlers.
+   This allows us to handle SIGSEGV signals generated when the
+   normal process stack is exhausted.  If this stack is not set
+   up (sigaltstack is unavailable or fails) and a SIGSEGV is
+   generated when the normal stack is exhausted then the program
+   will behave as though no SIGSEGV handler was installed.  */
+class alternate_signal_stack
+{
+public:
+  alternate_signal_stack ()
+  {
+#ifdef HAVE_SIGALTSTACK
+    m_stack.reset ((char *) xmalloc (SIGSTKSZ));
+
+    stack_t stack;
+    stack.ss_sp = m_stack.get ();
+    stack.ss_size = SIGSTKSZ;
+    stack.ss_flags = 0;
+
+    sigaltstack (&stack, &m_old_stack);
+#endif
+  }
+
+  ~alternate_signal_stack ()
+  {
+#ifdef HAVE_SIGALTSTACK
+    sigaltstack (&m_old_stack, nullptr);
+#endif
+  }
+
+  DISABLE_COPY_AND_ASSIGN (alternate_signal_stack);
+
+private:
+
+#ifdef HAVE_SIGALTSTACK
+  gdb::unique_xmalloc_ptr<char> m_stack;
+  stack_t m_old_stack;
+#endif
+};
+
+}
+
+#endif /* GDBSUPPORT_ALT_STACK_H */
--- a/gdb/gdbsupport/block-signals.h
+++ b/gdb/gdbsupport/block-signals.h
@@ -0,0 +1,65 @@
+/* Block signals used by gdb
+
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GDBSUPPORT_BLOCK_SIGNALS_H
+#define GDBSUPPORT_BLOCK_SIGNALS_H
+
+#include <signal.h>
+
+namespace gdb
+{
+
+/* This is an RAII class that temporarily blocks the signals needed by
+   gdb.  This can be used before starting a new thread to ensure that
+   this thread starts with the appropriate signals blocked.  */
+class block_signals
+{
+public:
+  block_signals ()
+  {
+#ifdef HAVE_PTHREAD_SIGMASK
+    sigset_t mask;
+    sigemptyset (&mask);
+    sigaddset (&mask, SIGINT);
+    sigaddset (&mask, SIGCHLD);
+    sigaddset (&mask, SIGALRM);
+    sigaddset (&mask, SIGWINCH);
+    pthread_sigmask (SIG_BLOCK, &mask, &m_old_mask);
+#endif
+  }
+
+  ~block_signals ()
+  {
+#ifdef HAVE_PTHREAD_SIGMASK
+    pthread_sigmask (SIG_SETMASK, &m_old_mask, nullptr);
+#endif
+  }
+
+  DISABLE_COPY_AND_ASSIGN (block_signals);
+
+private:
+
+#ifdef HAVE_PTHREAD_SIGMASK
+  sigset_t m_old_mask;
+#endif
+};
+
+}
+
+#endif /* GDBSUPPORT_BLOCK_SIGNALS_H */
--- a/gdb/gdbsupport/common.m4
+++ b/gdb/gdbsupport/common.m4
@@ -37,6 +37,37 @@ AC_DEFUN([GDB_AC_COMMON], [

  AC_CHECK_DECLS([strerror, strstr])

+  # Check for std::thread.  This does not work on some platforms, like
+  # mingw and DJGPP.
+  AC_LANG_PUSH([C++])
+  AX_PTHREAD([threads=yes], [threads=no])
+  if test "$threads" = "yes"; then
+    save_LIBS="$LIBS"
+    LIBS="$PTHREAD_LIBS $LIBS"
+    save_CXXFLAGS="$CXXFLAGS"
+    CXXFLAGS="$PTHREAD_CFLAGS $save_CFLAGS"
+    AC_CACHE_CHECK([for std::thread],
+		   gdb_cv_cxx_std_thread,
+		   [AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
+    [[#include <thread>
+      void callback() { }]],
+    [[std::thread t(callback);]])],
+				  gdb_cv_cxx_std_thread=yes,
+				  gdb_cv_cxx_std_thread=no)])
+
+    # This check must be here, while LIBS includes any necessary
+    # threading library.
+    AC_CHECK_FUNCS([pthread_sigmask pthread_setname_np])
+
+    LIBS="$save_LIBS"
+    CXXFLAGS="$save_CXXFLAGS"
+  fi
+  if test $gdb_cv_cxx_std_thread = yes; then
+    AC_DEFINE(CXX_STD_THREAD, 1,
+	      [Define to 1 if std::thread works.])
+  fi
+  AC_LANG_POP
+
  dnl Check if sigsetjmp is available.  Using AC_CHECK_FUNCS won't
  dnl do since sigsetjmp might only be defined as a macro.
 AC_CACHE_CHECK([for sigsetjmp], gdb_cv_func_sigsetjmp,
--- a/gdb/gdbsupport/gdb-sigmask.h
+++ b/gdb/gdbsupport/gdb-sigmask.h
@@ -0,0 +1,45 @@
+/* sigprocmask wrapper for gdb
+
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GDBSUPPORT_GDB_SIGMASK_H
+#define GDBSUPPORT_GDB_SIGMASK_H
+
+#include <signal.h>
+
+#ifdef HAVE_SIGPROCMASK
+
+#ifdef HAVE_PTHREAD_SIGMASK
+#define gdb_sigmask pthread_sigmask
+#else
+#define gdb_sigmask sigprocmask
+#endif
+
+#else /* HAVE_SIGPROCMASK */
+
+/* Other code checks HAVE_SIGPROCMASK, but if there happened to be a
+   system that only had pthread_sigmask, we could still use it with
+   some extra changes.  */
+#ifdef HAVE_PTHREAD_SIGMASK
+#error pthead_sigmask available without sigprocmask - please report
+#endif
+
+#endif /* HAVE_SIGPROCMASK */
+
+
+#endif /* GDBSUPPORT_GDB_SIGMASK_H */
--- a/gdb/gdbsupport/parallel-for.h
+++ b/gdb/gdbsupport/parallel-for.h
@@ -0,0 +1,83 @@
+/* Parallel for loops
+
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GDBSUPPORT_PARALLEL_FOR_H
+#define GDBSUPPORT_PARALLEL_FOR_H
+
+#include <algorithm>
+#if CXX_STD_THREAD
+#include <system_error>
+#include <thread>
+#include "gdbsupport/thread-pool.h"
+#endif
+
+namespace gdb
+{
+
+/* A very simple "parallel for".  This splits the range of iterators
+   into subranges, and then passes each subrange to the callback.  The
+   work may or may not be done in separate threads.
+
+   This approach was chosen over having the callback work on single
+   items because it makes it simple for the caller to do
+   once-per-subrange initialization and destruction.  */
+
+template<class RandomIt, class RangeFunction>
+void
+parallel_for_each (RandomIt first, RandomIt last, RangeFunction callback)
+{
+#if CXX_STD_THREAD
+  /* So we can use a local array below.  */
+  const size_t local_max = 16;
+  size_t n_threads = std::min (thread_pool::g_thread_pool->count (),
+			       local_max);
+  size_t n_actual_threads = 0;
+  std::future<void> futures[local_max];
+
+  size_t n_elements = last - first;
+  if (n_threads > 1 && 2 * n_threads <= n_elements)
+    {
+      size_t elts_per_thread = n_elements / n_threads;
+      n_actual_threads = n_threads - 1;
+      for (int i = 0; i < n_actual_threads; ++i)
+	{
+	  RandomIt end = first + elts_per_thread;
+	  auto task = [=] ()
+		      {
+			callback (first, end);
+		      };
+
+	  futures[i] = gdb::thread_pool::g_thread_pool->post_task (task);
+	  first = end;
+	}
+    }
+#endif /* CXX_STD_THREAD */
+
+  /* Process all the remaining elements in the main thread.  */
+  callback (first, last);
+
+#if CXX_STD_THREAD
+  for (int i = 0; i < n_actual_threads; ++i)
+    futures[i].wait ();
+#endif /* CXX_STD_THREAD */
+}
+
+}
+
+#endif /* GDBSUPPORT_PARALLEL_FOR_H */
--- a/gdb/gdbsupport/signals-state-save-restore.c
+++ b/gdb/gdbsupport/signals-state-save-restore.c
@@ -17,6 +17,7 @@

 #include "common-defs.h"
 #include "signals-state-save-restore.h"
+#include "gdbsupport/gdb-sigmask.h"

 #include <signal.h>

@@ -25,10 +26,6 @@
 #ifdef HAVE_SIGACTION
 static struct sigaction original_signal_actions[NSIG];

-/* Note that we use sigprocmask without worrying about threads because
-   the save/restore functions are called either from main, or after a
-   fork.  In both cases, we know the calling process is single
-   threaded.  */
 static sigset_t original_signal_mask;
 #endif

@@ -41,7 +38,7 @@ save_original_signals_state (bool quiet)
  int i;
  int res;

-  res = sigprocmask (0,  NULL, &original_signal_mask);
+  res = gdb_sigmask (0,  NULL, &original_signal_mask);
  if (res == -1)
    perror_with_name (("sigprocmask"));

@@ -110,7 +107,7 @@ restore_original_signals_state (void)
 	perror_with_name (("sigaction"));
    }

-  res = sigprocmask (SIG_SETMASK,  &original_signal_mask, NULL);
+  res = gdb_sigmask (SIG_SETMASK,  &original_signal_mask, NULL);
  if (res == -1)
    perror_with_name (("sigprocmask"));
 #endif
--- a/gdb/gdbsupport/thread-pool.c
+++ b/gdb/gdbsupport/thread-pool.c
@@ -0,0 +1,137 @@
+/* Thread pool
+
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "common-defs.h"
+#include "gdbsupport/thread-pool.h"
+#include "gdbsupport/alt-stack.h"
+#include "gdbsupport/block-signals.h"
+#include <algorithm>
+
+/* On the off chance that we have the pthread library on a Windows
+   host, but std::thread is not using it, avoid calling
+   pthread_setname_np on Windows.  */
+#ifndef _WIN32
+#ifdef HAVE_PTHREAD_SETNAME_NP
+#include <pthread.h>
+#endif
+#endif
+
+namespace gdb
+{
+
+/* The thread pool detach()s its threads, so that the threads will not
+   prevent the process from exiting.  However, it was discovered that
+   if any detached threads were still waiting on a condition variable,
+   then the condition variable's destructor would wait for the threads
+   to exit -- defeating the purpose.
+
+   Allocating the thread pool on the heap and simply "leaking" it
+   avoids this problem.
+*/
+thread_pool *thread_pool::g_thread_pool = new thread_pool ();
+
+thread_pool::~thread_pool ()
+{
+  /* Because this is a singleton, we don't need to clean up.  The
+     threads are detached so that they won't prevent process exit.
+     And, cleaning up here would be actively harmful in at least one
+     case -- see the comment by the definition of g_thread_pool.  */
+}
+
+void
+thread_pool::set_thread_count (size_t num_threads)
+{
+  std::lock_guard<std::mutex> guard (m_tasks_mutex);
+
+  /* If the new size is larger, start some new threads.  */
+  if (m_count < num_threads)
+    {
+      /* Ensure that signals used by gdb are blocked in the new
+	 threads.  */
+      block_signals blocker;
+      for (size_t i = m_count; i < num_threads; ++i)
+	{
+	  std::thread thread (&thread_pool::thread_function, this);
+#ifndef _WIN32 /* See the comment at the top of the file.  */
+#ifdef HAVE_PTHREAD_SETNAME_NP
+	  pthread_setname_np (thread.native_handle (), "gdb worker");
+#endif
+#endif
+	  thread.detach ();
+	}
+    }
+  /* If the new size is smaller, terminate some existing threads.  */
+  if (num_threads < m_count)
+    {
+      for (size_t i = num_threads; i < m_count; ++i)
+	m_tasks.emplace ();
+      m_tasks_cv.notify_all ();
+    }
+
+  m_count = num_threads;
+}
+
+std::future<void>
+thread_pool::post_task (std::function<void ()> func)
+{
+  std::packaged_task<void ()> t (func);
+  std::future<void> f = t.get_future ();
+
+  if (m_count == 0)
+    {
+      /* Just execute it now.  */
+      t ();
+    }
+  else
+    {
+      std::lock_guard<std::mutex> guard (m_tasks_mutex);
+      m_tasks.emplace (std::move (t));
+      m_tasks_cv.notify_one ();
+    }
+  return f;
+}
+
+void
+thread_pool::thread_function ()
+{
+  /* Ensure that SIGSEGV is delivered to an alternate signal
+     stack.  */
+  gdb::alternate_signal_stack signal_stack;
+
+  while (true)
+    {
+      task t;
+
+      {
+	/* We want to hold the lock while examining the task list, but
+	   not while invoking the task function.  */
+	std::unique_lock<std::mutex> guard (m_tasks_mutex);
+	while (m_tasks.empty ())
+	  m_tasks_cv.wait (guard);
+	t = std::move (m_tasks.front());
+	m_tasks.pop ();
+      }
+
+      if (!t.has_value ())
+	break;
+      (*t) ();
+    }
+}
+
+}
--- a/gdb/gdbsupport/thread-pool.h
+++ b/gdb/gdbsupport/thread-pool.h
@@ -0,0 +1,90 @@
+/* Thread pool
+
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GDBSUPPORT_THREAD_POOL_H
+#define GDBSUPPORT_THREAD_POOL_H
+
+#include <queue>
+#include <thread>
+#include <vector>
+#include <functional>
+#include <mutex>
+#include <condition_variable>
+#include <future>
+#include "gdbsupport/gdb_optional.h"
+
+namespace gdb
+{
+
+/* A thread pool.
+
+   There is a single global thread pool, see g_thread_pool.  Tasks can
+   be submitted to the thread pool.  They will be processed in worker
+   threads as time allows.  */
+class thread_pool
+{
+public:
+  /* The sole global thread pool.  */
+  static thread_pool *g_thread_pool;
+
+  ~thread_pool ();
+  DISABLE_COPY_AND_ASSIGN (thread_pool);
+
+  /* Set the thread count of this thread pool.  By default, no threads
+     are created -- the thread count must be set first.  */
+  void set_thread_count (size_t num_threads);
+
+  /* Return the number of executing threads.  */
+  size_t count () const
+  {
+    return m_count;
+  }
+
+  /* Post a task to the thread pool.  A future is returned, which can
+     be used to wait for the result.  */
+  std::future<void> post_task (std::function<void ()> func);
+
+private:
+
+  thread_pool () = default;
+
+  /* The callback for each worker thread.  */
+  void thread_function ();
+
+  /* An optional is used to represent a task.  If the optional is
+     empty, then this means that the receiving thread should
+     terminate.  If the optional is non-empty, then it is an actual
+     task to evaluate.  */
+  typedef optional<std::packaged_task<void ()>> task;
+
+  /* The current thread count.  */
+  size_t m_count = 0;
+
+  /* The tasks that have not been processed yet.  */
+  std::queue<task> m_tasks;
+
+  /* A condition variable and mutex that are used for communication
+     between the main thread and the worker threads.  */
+  std::condition_variable m_tasks_cv;
+  std::mutex m_tasks_mutex;
+};
+
+}
+
+#endif /* GDBSUPPORT_THREAD_POOL_H */
--- a/gdb/guile/guile.c
+++ b/gdb/guile/guile.c
@@ -36,6 +36,7 @@
 #include "guile-internal.h"
 #endif
 #include <signal.h>
+#include "gdbsupport/block-signals.h"

 /* The Guile version we're using.
   We *could* use the macros in libguile/version.h but that would preclude
@@ -798,10 +799,6 @@ _initialize_guile (void)

 #if HAVE_GUILE
  {
-#ifdef HAVE_SIGPROCMASK
-    sigset_t sigchld_mask, prev_mask;
-#endif
-
    /* The Python support puts the C side in module "_gdb", leaving the Python
       side to define module "gdb" which imports "_gdb".  There is evidently no
       similar convention in Guile so we skip this.  */
@@ -813,25 +810,20 @@ _initialize_guile (void)
    scm_set_automatic_finalization_enabled (0);
 #endif

-#ifdef HAVE_SIGPROCMASK
-    /* Before we initialize Guile, block SIGCHLD.
+    /* Before we initialize Guile, block signals needed by gdb
+       (especially SIGCHLD).
       This is done so that all threads created during Guile initialization
       have SIGCHLD blocked.  PR 17247.
       Really libgc and Guile should do this, but we need to work with
       libgc 7.4.x.  */
-    sigemptyset (&sigchld_mask);
-    sigaddset (&sigchld_mask, SIGCHLD);
-    sigprocmask (SIG_BLOCK, &sigchld_mask, &prev_mask);
-#endif
+    {
+      gdb::block_signals blocker;

-    /* scm_with_guile is the most portable way to initialize Guile.
-       Plus we need to initialize the Guile support while in Guile mode
-       (e.g., called from within a call to scm_with_guile).  */
-    scm_with_guile (call_initialize_gdb_module, NULL);
-
-#ifdef HAVE_SIGPROCMASK
-    sigprocmask (SIG_SETMASK, &prev_mask, NULL);
-#endif
+      /* scm_with_guile is the most portable way to initialize Guile.
+	 Plus we need to initialize the Guile support while in Guile mode
+	 (e.g., called from within a call to scm_with_guile).  */
+      scm_with_guile (call_initialize_gdb_module, NULL);
+    }

    /* Set Guile's backtrace to match the "set guile print-stack" default.
       [N.B. The two settings are still separate.]
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -67,6 +67,7 @@
 #include "nat/linux-namespaces.h"
 #include "gdbsupport/fileio.h"
 #include "gdbsupport/scope-exit.h"
+#include "gdbsupport/gdb-sigmask.h"

 /* This comment documents high-level logic of this file.

@@ -764,7 +765,7 @@ block_child_signals (sigset_t *prev_mask)
  if (!sigismember (&blocked_mask, SIGCHLD))
    sigaddset (&blocked_mask, SIGCHLD);

-  sigprocmask (SIG_BLOCK, &blocked_mask, prev_mask);
+  gdb_sigmask (SIG_BLOCK, &blocked_mask, prev_mask);
 }

 /* Restore child signals mask, previously returned by
@@ -773,7 +774,7 @@ block_child_signals (sigset_t *prev_mask)
 static void
 restore_child_signals_mask (sigset_t *prev_mask)
 {
-  sigprocmask (SIG_SETMASK, prev_mask, NULL);
+  gdb_sigmask (SIG_SETMASK, prev_mask, NULL);
 }

 /* Mask of signals to pass directly to the inferior.  */
@@ -4564,7 +4565,7 @@ Enables printf debugging output."),
  sigaction (SIGCHLD, &sigchld_action, NULL);

  /* Make sure we don't block SIGCHLD during a sigsuspend.  */
-  sigprocmask (SIG_SETMASK, NULL, &suspend_mask);
+  gdb_sigmask (SIG_SETMASK, NULL, &suspend_mask);
  sigdelset (&suspend_mask, SIGCHLD);

  sigemptyset (&blocked_mask);
--- a/gdb/main.c
+++ b/gdb/main.c
@@ -52,6 +52,7 @@
 #ifdef GDBTK
 #include "gdbtk/generic/gdbtk.h"
 #endif
+#include "gdbsupport/alt-stack.h"

 /* The selected interpreter.  This will be used as a set command
   variable, so it should always be malloc'ed - since
@@ -334,29 +335,6 @@ get_init_files (std::vector<std::string> *system_gdbinit,
  *local_gdbinit = localinit;
 }

-/* Try to set up an alternate signal stack for SIGSEGV handlers.
-   This allows us to handle SIGSEGV signals generated when the
-   normal process stack is exhausted.  If this stack is not set
-   up (sigaltstack is unavailable or fails) and a SIGSEGV is
-   generated when the normal stack is exhausted then the program
-   will behave as though no SIGSEGV handler was installed.  */
-
-static void
-setup_alternate_signal_stack (void)
-{
-#ifdef HAVE_SIGALTSTACK
-  stack_t ss;
-
-  /* FreeBSD versions older than 11.0 use char * for ss_sp instead of
-     void *.  This cast works with both types.  */
-  ss.ss_sp = (char *) xmalloc (SIGSTKSZ);
-  ss.ss_size = SIGSTKSZ;
-  ss.ss_flags = 0;
-
-  sigaltstack(&ss, NULL);
-#endif
-}
-
 /* Call command_loop.  */

 /* Prevent inlining this function for the benefit of GDB's selftests
@@ -898,7 +876,7 @@ captured_main_1 (struct captured_main_args *context)
  save_original_signals_state (quiet);

  /* Try to set up an alternate signal stack for SIGSEGV handlers.  */
-  setup_alternate_signal_stack ();
+  gdb::alternate_signal_stack signal_stack;

  /* Initialize all files.  */
  gdb_init (gdb_program_name);
--- a/gdb/maint.c
+++ b/gdb/maint.c
@@ -46,6 +46,10 @@
 #include "cli/cli-setshow.h"
 #include "cli/cli-cmds.h"

+#if CXX_STD_THREAD
+#include "gdbsupport/thread-pool.h"
+#endif
+
 static void maintenance_do_deprecate (const char *, int);

 /* Access the maintenance subcommands.  */
@@ -840,6 +844,37 @@ maintenance_set_profile_cmd (const char *args, int from_tty,
  error (_("Profiling support is not available on this system."));
 }
 #endif
+
+static int n_worker_threads = -1;
+
+/* Update the thread pool for the desired number of threads.  */
+static void
+update_thread_pool_size ()
+{
+#if CXX_STD_THREAD
+  int n_threads = n_worker_threads;
+
+  if (n_threads < 0)
+    {
+      n_threads = std::thread::hardware_concurrency ();
+      if (n_threads == 0)
+	{
+	  /* Meh.  */
+	  n_threads = 2;
+	}
+    }
+
+  gdb::thread_pool::g_thread_pool->set_thread_count (n_threads);
+#endif
+}
+
+static void
+maintenance_set_worker_threads (const char *args, int from_tty,
+				struct cmd_list_element *c)
+{
+  update_thread_pool_size ();
+}
+

 /* If true, display time usage both at startup and for each command.  */

@@ -1312,4 +1347,17 @@ When enabled GDB is profiled."),
 			   show_maintenance_profile_p,
 			   &maintenance_set_cmdlist,
 			   &maintenance_show_cmdlist);
+
+  add_setshow_zuinteger_unlimited_cmd ("worker-threads",
+				       class_maintenance,
+				       &n_worker_threads, _("\
+Set the number of worker threads GDB can use."), _("\
+Set the number of worker threads GDB can use."), _("\
+GDB may use multiple threads to speed up certain CPU-intensive operations,\n\
+such as demangling symbol names."),
+				       maintenance_set_worker_threads, NULL,
+				       &maintenance_set_cmdlist,
+				       &maintenance_show_cmdlist);
+
+  update_thread_pool_size ();
 }
--- a/gdb/minsyms.c
+++ b/gdb/minsyms.c
@@ -53,6 +53,11 @@
 #include "gdbsupport/symbol.h"
 #include <algorithm>
 #include "safe-ctype.h"
+#include "gdbsupport/parallel-for.h"
+
+#if CXX_STD_THREAD
+#include <mutex>
+#endif

 /* See minsyms.h.  */

@@ -136,12 +141,12 @@ msymbol_hash (const char *string)
 /* Add the minimal symbol SYM to an objfile's minsym hash table, TABLE.  */
 static void
 add_minsym_to_hash_table (struct minimal_symbol *sym,
-			  struct minimal_symbol **table)
+			  struct minimal_symbol **table,
+			  unsigned int hash_value)
 {
  if (sym->hash_next == NULL)
    {
-      unsigned int hash
-	= msymbol_hash (MSYMBOL_LINKAGE_NAME (sym)) % MINIMAL_SYMBOL_HASH_SIZE;
+      unsigned int hash = hash_value % MINIMAL_SYMBOL_HASH_SIZE;

      sym->hash_next = table[hash];
      table[hash] = sym;
@@ -152,18 +157,16 @@ add_minsym_to_hash_table (struct minimal_symbol *sym,
   TABLE.  */
 static void
 add_minsym_to_demangled_hash_table (struct minimal_symbol *sym,
-				    struct objfile *objfile)
+				    struct objfile_per_bfd_storage *per_bfd,
+				    unsigned int hash_value)
 {
  if (sym->demangled_hash_next == NULL)
    {
-      unsigned int hash = search_name_hash (MSYMBOL_LANGUAGE (sym),
-					    MSYMBOL_SEARCH_NAME (sym));
-
-      objfile->per_bfd->demangled_hash_languages.set (MSYMBOL_LANGUAGE (sym));
+      per_bfd->demangled_hash_languages.set (MSYMBOL_LANGUAGE (sym));

      struct minimal_symbol **table
-	= objfile->per_bfd->msymbol_demangled_hash;
-      unsigned int hash_index = hash % MINIMAL_SYMBOL_HASH_SIZE;
+	= per_bfd->msymbol_demangled_hash;
+      unsigned int hash_index = hash_value % MINIMAL_SYMBOL_HASH_SIZE;
      sym->demangled_hash_next = table[hash_index];
      table[hash_index] = sym;
    }
@@ -338,6 +341,7 @@ lookup_minimal_symbol (const char *name, const char *sfile,
 				  objfile_debug_name (objfile));
 	    }

+	  objfile->per_bfd->wait_for_msymbols ();
 	  /* Do two passes: the first over the ordinary hash table,
 	     and the second over the demangled hash table.  */
 	  lookup_minimal_symbol_mangled (name, sfile, objfile,
@@ -474,6 +478,7 @@ iterate_over_minimal_symbols
    (struct objfile *objf, const lookup_name_info &lookup_name,
     gdb::function_view<bool (struct minimal_symbol *)> callback)
 {
+  objf->per_bfd->wait_for_msymbols ();
  /* The first pass is over the ordinary hash table.  */
    {
      const char *name = linkage_name_str (lookup_name);
@@ -526,6 +531,7 @@ lookup_minimal_symbol_linkage (const char *name, struct objfile *objf)

  for (objfile *objfile : objf->separate_debug_objfiles ())
    {
+      objfile->per_bfd->wait_for_msymbols ();
      for (minimal_symbol *msymbol = objfile->per_bfd->msymbol_hash[hash];
 	   msymbol != NULL;
 	   msymbol = msymbol->hash_next)
@@ -559,6 +565,7 @@ lookup_minimal_symbol_text (const char *name, struct objfile *objf)
      if (objf == NULL || objf == objfile
 	  || objf == objfile->separate_debug_objfile_backlink)
 	{
+	  objfile->per_bfd->wait_for_msymbols ();
 	  for (msymbol = objfile->per_bfd->msymbol_hash[hash];
 	       msymbol != NULL && found_symbol.minsym == NULL;
 	       msymbol = msymbol->hash_next)
@@ -606,6 +613,7 @@ lookup_minimal_symbol_by_pc_name (CORE_ADDR pc, const char *name,
      if (objf == NULL || objf == objfile
 	  || objf == objfile->separate_debug_objfile_backlink)
 	{
+	  objfile->per_bfd->wait_for_msymbols ();
 	  for (msymbol = objfile->per_bfd->msymbol_hash[hash];
 	       msymbol != NULL;
 	       msymbol = msymbol->hash_next)
@@ -717,6 +725,7 @@ lookup_minimal_symbol_by_pc_section (CORE_ADDR pc_in, struct obj_section *sectio
      /* If this objfile has a minimal symbol table, go search it
         using a binary search.  */

+      objfile->per_bfd->wait_for_msymbols ();
      if (objfile->per_bfd->minimal_symbol_count > 0)
 	{
 	  int best_zero_sized = -1;
@@ -1127,7 +1136,12 @@ minimal_symbol_reader::record_full (gdb::string_view name,
  msymbol = &m_msym_bunch->contents[m_msym_bunch_index];
  symbol_set_language (msymbol, language_auto,
 		       &m_objfile->per_bfd->storage_obstack);
-  symbol_set_names (msymbol, name, copy_name, m_objfile->per_bfd);
+
+  if (copy_name)
+    msymbol->name = obstack_strndup (&m_objfile->per_bfd->storage_obstack,
+				     name.data (), name.size ());
+  else
+    msymbol->name = name.data ();

  SET_MSYMBOL_VALUE_ADDRESS (msymbol, address);
  MSYMBOL_SECTION (msymbol) = section;
@@ -1248,28 +1262,41 @@ clear_minimal_symbol_hash_tables (struct objfile *objfile)
    }
 }

+struct computed_hash_values
+{
+  size_t name_length;
+  hashval_t mangled_name_hash;
+  unsigned int minsym_hash;
+  unsigned int minsym_demangled_hash;
+};
+
 /* Build (or rebuild) the minimal symbol hash tables.  This is necessary
   after compacting or sorting the table since the entries move around
   thus causing the internal minimal_symbol pointers to become jumbled.  */
  
 static void
-build_minimal_symbol_hash_tables (struct objfile *objfile)
+build_minimal_symbol_hash_tables
+  (struct objfile_per_bfd_storage *per_bfd,
+   const std::vector<computed_hash_values>& hash_values)
 {
  int i;
  struct minimal_symbol *msym;

  /* (Re)insert the actual entries.  */
-  for ((i = objfile->per_bfd->minimal_symbol_count,
-	msym = objfile->per_bfd->msymbols.get ());
-       i > 0;
-       i--, msym++)
+  int mcount = per_bfd->minimal_symbol_count;
+  for ((i = 0,
+	msym = per_bfd->msymbols.get ());
+       i < mcount;
+       i++, msym++)
    {
      msym->hash_next = 0;
-      add_minsym_to_hash_table (msym, objfile->per_bfd->msymbol_hash);
+      add_minsym_to_hash_table (msym, per_bfd->msymbol_hash,
+				hash_values[i].minsym_hash);

      msym->demangled_hash_next = 0;
      if (MSYMBOL_SEARCH_NAME (msym) != MSYMBOL_LINKAGE_NAME (msym))
-	add_minsym_to_demangled_hash_table (msym, objfile);
+	add_minsym_to_demangled_hash_table
+	  (msym, per_bfd, hash_values[i].minsym_demangled_hash);
    }
 }

@@ -1290,8 +1317,11 @@ minimal_symbol_reader::install ()
  if (m_objfile->per_bfd->minsyms_read)
    return;

+
  if (m_msym_count > 0)
    {
+      m_objfile->per_bfd->wait_for_msymbols ();
+
      if (symtab_create_debug)
 	{
 	  fprintf_unfiltered (gdb_stdlog,
@@ -1354,7 +1384,71 @@ minimal_symbol_reader::install ()
      m_objfile->per_bfd->minimal_symbol_count = mcount;
      m_objfile->per_bfd->msymbols = std::move (msym_holder);

-      build_minimal_symbol_hash_tables (m_objfile);
+      msymbols = m_objfile->per_bfd->msymbols.get ();
+      objfile_per_bfd_storage* per_bfd = m_objfile->per_bfd;
+
+      m_objfile->per_bfd->m_minsym_future
+	= gdb::thread_pool::g_thread_pool->post_task ([msymbols, mcount,
+						      per_bfd] ()
+        {
+#if CXX_STD_THREAD
+	  /* Mutex that is used when modifying or accessing the demangled
+	     hash table.  */
+	  std::mutex demangled_mutex;
+#endif
+
+	  std::vector<computed_hash_values> hash_values (mcount);
+
+	  gdb::parallel_for_each
+	    (&msymbols[0], &msymbols[mcount],
+	     [&] (minimal_symbol *start, minimal_symbol *end)
+	     {
+	       for (minimal_symbol *msym = start; msym < end; ++msym)
+		 {
+		   size_t idx = msym - msymbols;
+		   hash_values[idx].name_length = strlen (msym->name);
+		   if (!msym->name_set)
+		     {
+		       /* This will be freed later, by symbol_set_names.  */
+		       char *demangled_name
+			 = symbol_find_demangled_name (msym, msym->name);
+		       symbol_set_demangled_name
+			 (msym, demangled_name,
+			  &per_bfd->storage_obstack);
+		       msym->name_set = 1;
+
+		       hash_values[idx].mangled_name_hash
+			 = fast_hash (msym->name, hash_values[idx].name_length);
+		     }
+		   hash_values[idx].minsym_hash
+		     = msymbol_hash (MSYMBOL_LINKAGE_NAME (msym));
+		   hash_values[idx].minsym_demangled_hash
+		     = search_name_hash (MSYMBOL_LANGUAGE (msym),
+					 MSYMBOL_SEARCH_NAME (msym));
+		 }
+	       {
+		 /* To limit how long we hold the lock, we only acquire it here
+		    and not while we demangle the names above.  */
+#if CXX_STD_THREAD
+		 std::lock_guard<std::mutex> guard (demangled_mutex);
+#endif
+		 for (minimal_symbol *msym = start; msym < end; ++msym)
+		   {
+		     size_t idx = msym - msymbols;
+		     symbol_set_names
+		       (msym,
+			gdb::string_view(msym->name,
+					 hash_values[idx].name_length),
+			false,
+			per_bfd,
+			hash_values[idx].mangled_name_hash);
+		   }
+	       }
+	     });
+
+	  build_minimal_symbol_hash_tables (per_bfd, hash_values);
+	}
+      );
    }
 }

@@ -1441,6 +1535,8 @@ minimal_symbol_upper_bound (struct bound_minimal_symbol minsym)
     other sections, to find the next symbol in this section with a
     different address.  */

+  minsym.objfile->per_bfd->wait_for_msymbols ();
+
  struct minimal_symbol *past_the_end
    = (minsym.objfile->per_bfd->msymbols.get ()
       + minsym.objfile->per_bfd->minimal_symbol_count);
--- a/gdb/objfiles.h
+++ b/gdb/objfiles.h
@@ -30,6 +30,9 @@
 #include "psymtab.h"
 #include <bitset>
 #include <vector>
+#if CXX_STD_THREAD
+#include <future>
+#endif
 #include "gdbsupport/next-iterator.h"
 #include "gdbsupport/safe-iterator.h"
 #include "bcache.h"
@@ -319,6 +322,19 @@ struct objfile_per_bfd_storage
  /* All the different languages of symbols found in the demangled
     hash table.  */
  std::bitset<nr_languages> demangled_hash_languages;
+
+  void wait_for_msymbols() {
+#if CXX_STD_THREAD
+    if (m_minsym_future.valid ())
+      {
+	m_minsym_future.wait ();
+	m_minsym_future = std::future<void> ();
+      }
+#endif
+  }
+#if CXX_STD_THREAD
+  std::future<void> m_minsym_future;
+#endif
 };

 /* An iterator that first returns a parent objfile, and then each
@@ -439,11 +455,13 @@ struct objfile

    minimal_symbol_iterator begin () const
    {
+      m_objfile->per_bfd->wait_for_msymbols ();
      return minimal_symbol_iterator (m_objfile->per_bfd->msymbols.get ());
    }

    minimal_symbol_iterator end () const
    {
+      m_objfile->per_bfd->wait_for_msymbols ();
      return minimal_symbol_iterator
 	(m_objfile->per_bfd->msymbols.get ()
 	 + m_objfile->per_bfd->minimal_symbol_count);
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -28,7 +28,6 @@
 #include "value.h"
 #include "language.h"
 #include "event-loop.h"
-#include "serial.h"
 #include "readline/tilde.h"
 #include "python.h"
 #include "extension-priv.h"
@@ -940,63 +939,81 @@ gdbpy_source_script (const struct extension_language_defn *extlang,

 /* Posting and handling events.  */

+/* A helper class to save and restore the GIL, but without touching
+   the other globals that are handled by gdbpy_enter.  */
+
+class gdbpy_gil
+{
+public:
+
+  gdbpy_gil ()
+    : m_state (PyGILState_Ensure ())
+  {
+  }
+
+  ~gdbpy_gil ()
+  {
+    PyGILState_Release (m_state);
+  }
+
+  DISABLE_COPY_AND_ASSIGN (gdbpy_gil);
+
+private:
+
+  PyGILState_STATE m_state;
+};
+
 /* A single event.  */
 struct gdbpy_event
 {
-  /* The Python event.  This is just a callable object.  */
-  PyObject *event;
-  /* The next event.  */
-  struct gdbpy_event *next;
+  gdbpy_event (gdbpy_ref<> &&func)
+    : m_func (func.release ())
+  {
+  }
+
+  gdbpy_event (gdbpy_event &&other)
+    : m_func (other.m_func)
+  {
+    other.m_func = nullptr;
+  }
+
+  gdbpy_event (const gdbpy_event &other)
+    : m_func (other.m_func)
+  {
+    gdbpy_gil gil;
+    Py_XINCREF (m_func);
+  }
+
+  ~gdbpy_event ()
+  {
+    gdbpy_gil gil;
+    Py_XDECREF (m_func);
+  }
+
+  gdbpy_event &operator= (const gdbpy_event &other) = delete;
+
+  void operator() ()
+  {
+    gdbpy_enter enter_py (get_current_arch (), current_language);
+
+    gdbpy_ref<> call_result (PyObject_CallObject (m_func, NULL));
+    if (call_result == NULL)
+      gdbpy_print_stack ();
+  }
+
+private:
+
+  /* The Python event.  This is just a callable object.  Note that
+     this is not a gdbpy_ref<>, because we have to take particular
+     care to only destroy the reference when holding the GIL. */
+  PyObject *m_func;
 };

-/* All pending events.  */
-static struct gdbpy_event *gdbpy_event_list;
-/* The final link of the event list.  */
-static struct gdbpy_event **gdbpy_event_list_end;
-
-/* So that we can wake up the main thread even when it is blocked in
-   poll().  */
-static struct serial_event *gdbpy_serial_event;
-
-/* The file handler callback.  This reads from the internal pipe, and
-   then processes the Python event queue.  This will always be run in
-   the main gdb thread.  */
-
-static void
-gdbpy_run_events (int error, gdb_client_data client_data)
-{
-  gdbpy_enter enter_py (get_current_arch (), current_language);
-
-  /* Clear the event fd.  Do this before flushing the events list, so
-     that any new event post afterwards is sure to re-awake the event
-     loop.  */
-  serial_event_clear (gdbpy_serial_event);
-
-  while (gdbpy_event_list)
-    {
-      /* Dispatching the event might push a new element onto the event
-	 loop, so we update here "atomically enough".  */
-      struct gdbpy_event *item = gdbpy_event_list;
-      gdbpy_event_list = gdbpy_event_list->next;
-      if (gdbpy_event_list == NULL)
-	gdbpy_event_list_end = &gdbpy_event_list;
-
-      gdbpy_ref<> call_result (PyObject_CallObject (item->event, NULL));
-      if (call_result == NULL)
-	gdbpy_print_stack ();
-
-      Py_DECREF (item->event);
-      xfree (item);
-    }
-}
-
 /* Submit an event to the gdb thread.  */
 static PyObject *
 gdbpy_post_event (PyObject *self, PyObject *args)
 {
-  struct gdbpy_event *event;
  PyObject *func;
-  int wakeup;

  if (!PyArg_ParseTuple (args, "O", &func))
    return NULL;
@@ -1010,36 +1027,13 @@ gdbpy_post_event (PyObject *self, PyObject *args)

  Py_INCREF (func);

-  /* From here until the end of the function, we have the GIL, so we
-     can operate on our global data structures without worrying.  */
-  wakeup = gdbpy_event_list == NULL;
-
-  event = XNEW (struct gdbpy_event);
-  event->event = func;
-  event->next = NULL;
-  *gdbpy_event_list_end = event;
-  gdbpy_event_list_end = &event->next;
-
-  /* Wake up gdb when needed.  */
-  if (wakeup)
-    serial_event_set (gdbpy_serial_event);
+  gdbpy_ref<> func_ref = gdbpy_ref<>::new_reference (func);
+  gdbpy_event event (std::move (func_ref));
+  run_on_main_thread (event);

  Py_RETURN_NONE;
 }

-/* Initialize the Python event handler.  */
-static int
-gdbpy_initialize_events (void)
-{
-  gdbpy_event_list_end = &gdbpy_event_list;
-
-  gdbpy_serial_event = make_serial_event ();
-  add_file_handler (serial_event_fd (gdbpy_serial_event),
-		    gdbpy_run_events, NULL);
-
-  return 0;
-}
-


 /* This is the extension_language_ops.before_prompt "method".  */
@@ -1704,7 +1698,6 @@ do_start_initialization ()
      || gdbpy_initialize_linetable () < 0
      || gdbpy_initialize_thread () < 0
      || gdbpy_initialize_inferior () < 0
-      || gdbpy_initialize_events () < 0
      || gdbpy_initialize_eventregistry () < 0
      || gdbpy_initialize_py_events () < 0
      || gdbpy_initialize_event () < 0
--- a/gdb/ser-event.c
+++ b/gdb/ser-event.c
@@ -20,6 +20,10 @@
 #include "ser-event.h"
 #include "serial.h"
 #include "gdbsupport/filestuff.h"
+#if CXX_STD_THREAD
+#include <mutex>
+#endif
+#include "event-loop.h"

 /* On POSIX hosts, a serial_event is basically an abstraction for the
   classical self-pipe trick.
@@ -217,3 +221,77 @@ serial_event_clear (struct serial_event *event)
  ResetEvent (state->event);
 #endif
 }
+
+
+
+/* The serial event used when posting runnables.  */
+
+static struct serial_event *runnable_event;
+
+/* Runnables that have been posted.  */
+
+static std::vector<std::function<void ()>> runnables;
+
+#if CXX_STD_THREAD
+
+/* Mutex to hold when handling runnable_event or runnables.  */
+
+static std::mutex runnable_mutex;
+
+#endif
+
+/* Run all the queued runnables.  */
+
+static void
+run_events (int error, gdb_client_data client_data)
+{
+  std::vector<std::function<void ()>> local;
+
+  /* Hold the lock while changing the globals, but not while running
+     the runnables.  */
+  {
+#if CXX_STD_THREAD
+    std::lock_guard<std::mutex> lock (runnable_mutex);
+#endif
+
+    /* Clear the event fd.  Do this before flushing the events list,
+       so that any new event post afterwards is sure to re-awaken the
+       event loop.  */
+    serial_event_clear (runnable_event);
+
+    /* Move the vector in case running a runnable pushes a new
+       runnable.  */
+    local = std::move (runnables);
+  }
+
+  for (auto &item : local)
+    {
+      try
+	{
+	  item ();
+	}
+      catch (...)
+	{
+	  /* Ignore exceptions in the callback.  */
+	}
+    }
+}
+
+/* See ser-event.h.  */
+
+void
+run_on_main_thread (std::function<void ()> &&func)
+{
+#if CXX_STD_THREAD
+  std::lock_guard<std::mutex> lock (runnable_mutex);
+#endif
+  runnables.emplace_back (std::move (func));
+  serial_event_set (runnable_event);
+}
+
+void
+_initialize_ser_event ()
+{
+  runnable_event = make_serial_event ();
+  add_file_handler (serial_event_fd (runnable_event), run_events, nullptr);
+}
--- a/gdb/ser-event.h
+++ b/gdb/ser-event.h
@@ -19,6 +19,8 @@
 #ifndef SER_EVENT_H
 #define SER_EVENT_H

+#include <functional>
+
 /* This is used to be able to signal the event loop (or any other
   select/poll) of events, in a race-free manner.

@@ -48,4 +50,8 @@ extern void serial_event_set (struct serial_event *event);
   call is made.  */
 extern void serial_event_clear (struct serial_event *event);

+/* Send a runnable to the main thread.  */
+
+extern void run_on_main_thread (std::function<void ()> &&);
+
 #endif
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -770,20 +770,23 @@ create_demangled_names_hash (struct objfile_per_bfd_storage *per_bfd)
  /* Choose 256 as the starting size of the hash table, somewhat arbitrarily.
     The hash table code will round this up to the next prime number.
     Choosing a much larger table size wastes memory, and saves only about
-     1% in symbol reading.  */
+     1% in symbol reading.  However, if the minsym count is already
+     initialized (e.g. because symbol name setting was deferred to
+     a background thread) we can initialize the hashtable with that
+     count, because we will almost certainly have at least that
+     many entries.  If we have a nonzero number but less than 256,
+     we still stay with 256 to have some space for psymbols, etc.  */
+
+  int count = std::max (per_bfd->minimal_symbol_count, 256);

  per_bfd->demangled_names_hash.reset (htab_create_alloc
-    (256, hash_demangled_name_entry, eq_demangled_name_entry,
+    (count, hash_demangled_name_entry, eq_demangled_name_entry,
     free_demangled_name_entry, xcalloc, xfree));
 }

-/* Try to determine the demangled name for a symbol, based on the
-   language of that symbol.  If the language is set to language_auto,
-   it will attempt to find any demangling algorithm that works and
-   then set the language appropriately.  The returned name is allocated
-   by the demangler and should be xfree'd.  */
+/* See symtab.h  */

-static char *
+char *
 symbol_find_demangled_name (struct general_symbol_info *gsymbol,
 			    const char *mangled)
 {
@@ -830,7 +833,8 @@ symbol_find_demangled_name (struct general_symbol_info *gsymbol,
 void
 symbol_set_names (struct general_symbol_info *gsymbol,
 		  gdb::string_view linkage_name, bool copy_name,
-		  struct objfile_per_bfd_storage *per_bfd)
+		  struct objfile_per_bfd_storage *per_bfd,
+		  gdb::optional<hashval_t> hash)
 {
  struct demangled_name_entry **slot;

@@ -858,9 +862,11 @@ symbol_set_names (struct general_symbol_info *gsymbol,
    create_demangled_names_hash (per_bfd);

  struct demangled_name_entry entry (linkage_name);
+  if (!hash.has_value ())
+    hash = hash_demangled_name_entry (&entry);
  slot = ((struct demangled_name_entry **)
-	  htab_find_slot (per_bfd->demangled_names_hash.get (),
-			  &entry, INSERT));
+          htab_find_slot_with_hash (per_bfd->demangled_names_hash.get (),
+				    &entry, *hash, INSERT));

  /* If this name is not in the hash table, add it.  */
  if (*slot == NULL
@@ -884,8 +890,15 @@ symbol_set_names (struct general_symbol_info *gsymbol,
      else
 	linkage_name_copy = linkage_name;

-      gdb::unique_xmalloc_ptr<char> demangled_name_ptr
-	(symbol_find_demangled_name (gsymbol, linkage_name_copy.data ()));
+      /* The const_cast is safe because the only reason it is already
+         initialized is if we purposefully set it from a background
+         thread to avoid doing the work here.  However, it is still
+         allocated from the heap and needs to be freed by us, just
+         like if we called symbol_find_demangled_name here.  */
+      gdb::unique_xmalloc_ptr<char> demangled_name
+	(gsymbol->language_specific.demangled_name
+	 ? const_cast<char *> (gsymbol->language_specific.demangled_name)
+	 : symbol_find_demangled_name (gsymbol, linkage_name_copy.data ()));

      /* Suppose we have demangled_name==NULL, copy_name==0, and
 	 linkage_name_copy==linkage_name.  In this case, we already have the
@@ -919,7 +932,7 @@ symbol_set_names (struct general_symbol_info *gsymbol,
 	  new (*slot) demangled_name_entry
 	    (gdb::string_view (mangled_ptr, linkage_name.length ()));
 	}
-      (*slot)->demangled = std::move (demangled_name_ptr);
+      (*slot)->demangled = std::move (demangled_name);
      (*slot)->language = gsymbol->language;
    }
  else if (gsymbol->language == language_unknown
--- a/gdb/symtab.h
+++ b/gdb/symtab.h
@@ -503,6 +503,16 @@ extern void symbol_set_language (struct general_symbol_info *symbol,
                                 enum language language,
 				 struct obstack *obstack);

+
+/* Try to determine the demangled name for a symbol, based on the
+   language of that symbol.  If the language is set to language_auto,
+   it will attempt to find any demangling algorithm that works and
+   then set the language appropriately.  The returned name is allocated
+   by the demangler and should be xfree'd.  */
+
+extern char *symbol_find_demangled_name (struct general_symbol_info *gsymbol,
+					 const char *mangled);
+
 /* Set just the linkage name of a symbol; do not try to demangle
   it.  Used for constructs which do not have a mangled name,
   e.g. struct tags.  Unlike SYMBOL_SET_NAMES, linkage_name must
@@ -519,7 +529,9 @@ extern void symbol_set_language (struct general_symbol_info *symbol,
 		    (objfile)->per_bfd)
 extern void symbol_set_names (struct general_symbol_info *symbol,
 			      gdb::string_view linkage_name, bool copy_name,
-			      struct objfile_per_bfd_storage *per_bfd);
+			      struct objfile_per_bfd_storage *per_bfd,
+			      gdb::optional<hashval_t> hash
+			        = gdb::optional<hashval_t> ());

 /* Now come lots of name accessor macros.  Short version as to when to
   use which: Use SYMBOL_NATURAL_NAME to refer to the name of the
@@ -698,6 +710,10 @@ struct minimal_symbol : public general_symbol_info

  unsigned maybe_copied : 1;

+  /* Non-zero if this symbol ever had its demangled name set (even if
+     it was set to NULL).  */
+  unsigned int name_set : 1;
+
  /* Minimal symbols with the same hash key are kept on a linked
     list.  This is the link.  */

--- a/gdb/unittests/main-thread-selftests.c
+++ b/gdb/unittests/main-thread-selftests.c
@@ -0,0 +1,80 @@
+/* Self tests for run_on_main_thread
+
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include "gdbsupport/selftest.h"
+#include "gdbsupport/block-signals.h"
+#include "ser-event.h"
+#include "event-loop.h"
+#if CXX_STD_THREAD
+#include <thread>
+#endif
+
+namespace selftests {
+namespace main_thread_tests {
+
+#if CXX_STD_THREAD
+
+static bool done;
+
+static void
+set_done ()
+{
+  run_on_main_thread ([] ()
+    {
+      done = true;
+    });
+}
+
+static void
+run_tests ()
+{
+  std::thread thread;
+
+  done = false;
+
+  {
+    gdb::block_signals blocker;
+
+    thread = std::thread (set_done);
+  }
+
+  while (!done && gdb_do_one_event () >= 0)
+    ;
+
+  /* Actually the test will just hang, but we want to test
+     something.  */
+  SELF_CHECK (done);
+
+  thread.join ();
+}
+
+#endif
+
+}
+}
+
+void
+_initialize_main_thread_selftests ()
+{
+#if CXX_STD_THREAD
+  selftests::register_test ("main_thread",
+			    selftests::main_thread_tests::run_tests);
+#endif
+}
Author	SHA1	Message	Date
Christian Biesinger	12f4dc41bf	[RFC] Don't block on finishing demangling msymbols Instead, do it all on a background thread and only block when we actually need the result. Note, this is a speedup but not quite as much as I was expecting; still looking into what causes the waits. However, let me know if you have thoughts on the concept! Change-Id: I9d871917459ece0b41d31670b3c56600757aea66	2019-11-18 17:51:10 -06:00
Christian Biesinger	6f509f2489	Create a correctly-sized demangled names hashtable If we have a minsym count, we know the demangled names hashtable will be at least that big. So use that count to create it, so we don't have to resize/rehash it as much. This is a 6% improvement in minsym loading time. 2019-11-18 Christian Biesinger <cbiesinger@google.com> * symtab.c (create_demangled_names_hash): Use per_bfd-> minimal_symbol_count as the initial size, if greater than our default size. Change-Id: I1f074d38e1d90af58705ec852f90c84cc034cd2e	2019-11-18 17:51:10 -06:00
Christian Biesinger	f445b98611	Compute msymbol hash codes in parallel This is for the msymbol_hash and msymbol_demangled_hash hashtables in objfile_per_bfd_storage. This basically computes those hash codes together with the demangled symbol name in the background, before it inserts the symbols in the hash table. gdb/ChangeLog: 2019-09-30 Christian Biesinger <cbiesinger@google.com> * minsyms.c (add_minsym_to_hash_table): Use a previously computed hash code if possible. (add_minsym_to_demangled_hash_table): Likewise. (minimal_symbol_reader::install): Compute the hash codes for msymbol on the background thread. * symtab.h (struct minimal_symbol) <hash_value, demangled_hash_value>: Add these fields. Change-Id: Ifaa3346e9998f05743bff9e2eaad3f83b954d071	2019-11-10 12:30:24 -06:00
Christian Biesinger	65ffb7c552	Precompute hash value for symbol_set_names We can also compute the hash for the mangled name on a background thread so make this function even faster (about a 7% speedup). gdb/ChangeLog: 2019-10-03 Christian Biesinger <cbiesinger@google.com> * minsyms.c (minimal_symbol_reader::install): Also compute the hash of the mangled name on the background thread. * symtab.c (symbol_set_names): Allow passing in the hash of the linkage_name. * symtab.h (symbol_set_names): Likewise. Change-Id: I044449e7eb60cffc1c43efd3412f2b485bd9faac	2019-11-10 12:30:24 -06:00
Tom Tromey	4a7dabea39	Set names of worker threads This adds some configury so that gdb can set the names of worker threads. This makes them show up more nicely when debugging gdb itself. 2019-10-19 Tom Tromey <tom@tromey.com> * gdbsupport/thread-pool.c (thread_pool::set_thread_count): Set name of worker thread. * gdbsupport/common.m4 (GDB_AC_COMMON): Check for pthread_setname_np. * configure, config.in: Rebuild. gdb/gdbserver/ChangeLog 2019-10-19 Tom Tromey <tom@tromey.com> * configure, config.in: Rebuild. Change-Id: I60473d65ae9ae14d8c56ddde39684240c16aaf35	2019-11-10 10:44:50 -07:00
Tom Tromey	e4efbf384e	Use run_on_main_thread in gdb.post_event This changes gdb.post_event to use the new run_on_main_thread function. This is somewhat tricky because the Python GIL must be held while manipulating reference counts. 2019-10-19 Tom Tromey <tom@tromey.com> * python/python.c (class gdbpy_gil): New. (struct gdbpy_event): Add constructor, destructor, operator(). (gdbpy_post_event): Use run_on_main_thread. (gdbpy_initialize_events): Remove. (do_start_initialization): Update. Change-Id: Ie4431e60f328dae48bd96b6c6a8e875e70bda1de	2019-11-10 10:44:50 -07:00
Tom Tromey	9ca863ae09	Add maint set/show worker-threads This adds maint commands to control the number of worker threads that gdb can use. 2019-10-19 Tom Tromey <tom@tromey.com> * NEWS: Add entry. * maint.c (_initialize_maint_cmds): Add "worker-threads" maint commands. Call update_thread_pool_size. (update_thread_pool_size, maintenance_set_worker_threads): New functions. (n_worker_threads): New global. gdb/doc/ChangeLog 2019-10-19 Tom Tromey <tom@tromey.com> * gdb.texinfo (Maintenance Commands): Document new maint commands. Change-Id: I4fb514faa05879d8afe62c77036a4469d57dca2a	2019-11-10 10:44:50 -07:00
Tom Tromey	15ae80b467	Demangle minsyms in parallel This patch introduces a simple parallel for_each and changes the minimal symbol reader to use it when computing the demangled name for a minimal symbol. This yields a speedup when reading minimal symbols. 2019-10-19 Christian Biesinger <cbiesinger@google.com> Tom Tromey <tom@tromey.com> * minsyms.c (minimal_symbol_reader::install): Use parallel_for_each. * gdbsupport/parallel-for.h: New file. * Makefile.in (HFILES_NO_SRCDIR): Add gdbsupport/parallel-for.h. Change-Id: I220341f70e94dd02df5dd424272c50a5afb64978	2019-11-10 10:44:50 -07:00
Christian Biesinger	b0ca8b4f16	Implement a thread pool This adds a simple thread pool to gdb. In the end, this seemed preferable to the approach taken in an earlier version of this series; namely, starting threads in the parallel-foreach implementation. This approach reduces the overhead of starting new threads, and also lets the user control (in a subsequent patch) exactly how many worker threads are running. 2019-10-19 Christian Biesinger <cbiesinger@google.com> Tom Tromey <tom@tromey.com> * gdbsupport/thread-pool.h: New file. * gdbsupport/thread-pool.c: New file. * Makefile.in (COMMON_SFILES): Add thread-pool.c. (HFILES_NO_SRCDIR): Add thread-pool.h. Change-Id: I597bb642780cb9d578ca92373d2a638efb44fe52	2019-11-10 10:44:49 -07:00
Tom Tromey	af2deea454	Introduce thread-safe way to handle SIGSEGV The gdb demangler installs a SIGSEGV handler in order to protect gdb from demangler bugs. However, this is not thread-safe, as signal handlers are global to the process. This patch changes gdb to always install a global SIGSEGV handler, and then lets threads indicate their interest in handling the signal by setting a thread-local variable. This patch then arranges for the demangler code to use this; being sure to arrange for calls to warning and the like to be done on the main thread. One thing I wondered while writing this patch is if there are any systems that do not have "sigaction". If gdb could assume this, it would simplify this code. 2019-10-19 Tom Tromey <tom@tromey.com> * event-top.h (thread_local_segv_handler): Declare. * event-top.c (thread_local_segv_handler): New global. (install_handle_sigsegv, handle_sigsegv): New functions. (async_init_signals): Install SIGSEGV handler. * cp-support.c (gdb_demangle_jmp_buf): Change type. Now thread-local. (report_failed_demangle): New function. (gdb_demangle): Make core_dump_allowed atomic. Remove signal handler-setting code, instead use segv_handler. Run warning code on main thread. Change-Id: Ic832bbb033b64744e4b44f14b41db7e4168ce427	2019-11-10 10:44:49 -07:00
Tom Tromey	fe29e1fcde	Introduce run_on_main_thread This introduces a way for a callback to be run on the main thread. 2019-10-19 Tom Tromey <tom@tromey.com> * unittests/main-thread-selftests.c: New file. * Makefile.in (SUBDIR_UNITTESTS_SRCS): Add main-thread-selftests.c. * ser-event.h (run_on_main_thread): Declare. * ser-event.c (runnable_event, runnables, runnable_mutex): New globals. (run_events, run_on_main_thread, _initialize_ser_event): New functions. Change-Id: I16ef82f0564e9f8a524bdc64cb31df79a988ad9f	2019-11-10 10:44:49 -07:00
Tom Tromey	d14a705ab9	Introduce alternate_signal_stack RAII class This introduces a new RAII class that temporarily installs an alternate signal stack (on systems that have sigaltstack); then changes the one gdb use of sigaltstack to use this class instead. This will be used in a later patch, when creating new threads that may want to handle SIGSEGV. 2019-10-19 Tom Tromey <tom@tromey.com> * main.c (setup_alternate_signal_stack): Remove. (captured_main_1): Use gdb::alternate_signal_stack. * gdbsupport/alt-stack.h: New file. Change-Id: I721c047ae9d51a35fd274a6dbc00a58c6440dae6	2019-11-10 10:44:49 -07:00
Tom Tromey	530c45db24	Add RAII class for blocking gdb signals This adds configury support and an RAII class that can be used to temporarily block signals that are used by gdb. (This class is not used in this patch, but it split out for easier review.) The idea of this patch is that these signals should only be delivered to the main thread. So, when creating a background thread, they are temporarily blocked; the blocked state is inherited by the new thread. The sigprocmask man page says: The use of sigprocmask() is unspecified in a multithreaded process; see pthread_sigmask(3). This patch changes gdb to use pthread_sigmask when appropriate, by introducing a convenience define. I've updated gdbserver as well, because I had to touch gdbsupport, and because the threading patches will make it link against the thread library. I chose not to touch the NTO code, because I don't know anything about that platform and because I cannot test it. Finally, this modifies an existing spot in the Guile layer to use the new facility. 2019-10-19 Tom Tromey <tom@tromey.com> * gdbsupport/signals-state-save-restore.c (original_signal_mask): Remove comment. (save_original_signals_state, restore_original_signals_state): Use gdb_sigmask. * linux-nat.c (block_child_signals, restore_child_signals_mask) (_initialize_linux_nat): Use gdb_sigmask. * guile/guile.c (_initialize_guile): Use block_signals. * Makefile.in (HFILES_NO_SRCDIR): Add gdb-sigmask.h. * gdbsupport/gdb-sigmask.h: New file. * event-top.c (async_sigtstp_handler): Use gdb_sigmask. * cp-support.c (gdb_demangle): Use gdb_sigmask. * gdbsupport/common.m4 (GDB_AC_COMMON): Check for pthread_sigmask. * configure, config.in: Rebuild. * gdbsupport/block-signals.h: New file. gdb/gdbserver/ChangeLog 2019-10-19 Tom Tromey <tom@tromey.com> * remote-utils.c (block_unblock_async_io): Use gdb_sigmask. * linux-low.c (linux_wait_for_event_filtered, linux_async): Use gdb_sigmask. * configure, config.in: Rebuild. Change-Id: If3f37dc57dd859c226e9e4d79458a0514746e8c6	2019-11-10 10:44:49 -07:00
Tom Tromey	a7231e9d1c	Add configure check for std::thread This adds a configure check for std::thread. This is needed because std::thread is not available on some systems, like some versions of mingw and DJGPP. This also adds configury to make sure that a threaded gdb links against the correct threading library (-lpthread or the like), and passes the right flags (e.g., -pthread) to the compilations. Note that this also links gdbserver against the thread library. This is not strictly necessary at this point in the series, but a later patch will change gdbsupport to use pthread_sigmask, at which point this will be needed. 2019-10-19 Tom Tromey <tom@tromey.com> * acinclude.m4: Include ax_pthread.m4. * Makefile.in (PTHREAD_CFLAGS, PTHREAD_LIBS): New variables. (INTERNAL_CFLAGS_BASE): Use PTHREAD_CFLAGS. (CLIBS): Use PTHREAD_LIBS. (aclocal_m4_deps): Add ax_pthread.m4. * config.in, configure: Rebuild. * gdbsupport/common.m4 (GDB_AC_COMMON): Check for std::thread. gdb/gdbserver/ChangeLog 2019-10-19 Tom Tromey <tom@tromey.com> * Makefile.in (PTHREAD_CFLAGS, PTHREAD_LIBS): New variables. (INTERNAL_CFLAGS_BASE): Use PTHREAD_CFLAGS. (GDBSERVER_LIBS): Use PTHREAD_LIBS. * acinclude.m4: Include ax_pthread.m4. * config.in, configure: Rebuild. Change-Id: I00ec55db6077f2615421a93461fc3be57e916aa0	2019-11-10 10:44:49 -07:00
Tom Tromey	bb749d8ae3	Defer minimal symbol name-setting Currently the demangled name of a minimal symbol is set when creating the symbol. However, there is no intrinsic need to do this. This patch instead arranges for the demangling to be done just before the minsym hash tables are filled. This will be useful in a later patch. gdb/ChangeLog 2019-10-19 Tom Tromey <tom@tromey.com> * symtab.h (struct minimal_symbol) <name_set>: New member. * minsyms.c (minimal_symbol_reader::record_full): Copy name. Don't call symbol_set_names. (minimal_symbol_reader::install): Call symbol_set_names. Change-Id: I4fe3993b99fb3a43968067806e294d48e377fd76	2019-11-10 10:44:49 -07:00